Why Did the Person Who Recovered from Skin Disease Offer Atoning Sacrifices?

I've been reading Leviticus 13-14 for my weekly quiet time, and these are chapters on skin disease.  One question that comes up in my reading of scholarly discussions of these chapters concerns why the person who was being purified after having the skin disease had to offer a guilt offering and a sin offering.  Did he do something wrong?  In this post, I'll refer to two interactions with this issue that I came across.

1.  The Intervarsity Press Bible Background Commentary: Old Testament----which is written by John Walton (of The Lost World of Genesis 1 fame), Victor Matthews, and Mark Chavalas----says the following about Leviticus 14:12:

"guilt offering.  This offering, better translated 'reparation offering,' is described in chapter 5.  It is generally offered when the sanctuary has somehow suffered loss.  It may be part of this ritual to make amends for any offerings that had to be omitted by the individual during his quarantine.  Another suggestion is that since skin affliction could at times be a punishment from God for an act of sacrilege, the reparation offering is made just in case there was some such offense that the victim was unaware of."

This comment mentions two suggestions.  The first suggestion is that the person who has recovered from skin disease is offering a guilt offering to atone for the offerings that he did not give to the sanctuary when he was recovering outside of the camp of Israel.  This did not make much sense to me at first, for my impression was that the average Israelite was not required to sacrifice a burnt offering-----the priests had to do so daily, but the average Israelite did so when he wanted.  But, on second thought, I recalled that there were things that the average Israelites were required to give to the sanctuary or to God: the firstborn of their animals, the firstfruits of their crops, tithes, sin offerings when they sinned unintentionally, and guilt offerings when they transgressed in certain areas.  Consequently, it makes sense to me that an Israelite who recovered from skin disease would have to make up for what he could not give to the sanctuary when he was indisposed.

The second suggestion is that the Israelite could have been struck with a skin disease on account of some sin that he committed, and so the guilt offering is designed to atone for that just in case that's true.  This is a rabbinic position----only my impression is that ancient rabbis went further and held that the skin disease definitely was God's punishment for sin, rather than just saying that it could have been a punishment.  Miriam was an example of one who spoke evil against Moses and was punished with a skin disease (Numbers 12).

2.  Jacob Milgrom in The HarperCollins Study Bible states the following about Leviticus 14:10-20:
"The final stage of his purification takes place the following day when he brings a reparation offering for having possibly desecrated a sacred object or space (see 5.17-19)...; a purification offering (not properly sin offering) for having contaminated the sanctuary by his impurity...and a burnt offering and a grain offering to expiate for neglected performative commandments or sinful thoughts..."

Milgrom is saying that the recovered person offers the guilt offering to atone for having desecrated a sacred object or space, and the reason is that Leviticus 5:17-19 commands the guilt offering to be offered for that sort of thing.  On a similar note, Baruch Schwartz in the Jewish Study Bible refers to II Chronicles 26:16-19, in which King Uzziah is stricken with a skin disease because he had entered the sanctuary to burn incense, something that only priests were permitted to do.  Milgrom is probably arguing that the person was believed to have been afflicted with skin disease as punishment for having committed an act of sacrilege.

I'd probably need to do a deeper study of the sin offering to understand Milgrom's point on that.  Milgrom says that the recovered person offers the purification offering (or sin offering) to atone for polluting the sanctuary with his skin disease----for a presumption behind the purity system is that ritual impurity travels from the Israelite to the sanctuary and contaminates it (see Numbers 19:13, 20).  Because the sin offering is commanded for unintentional sins, however----for unwittingly transgressing God's law----I wonder if and how that relates to ritual impurity, which pertains to things that appear to be involuntary (i.e., skin disease----unless you see that as punishment for sin, having an involuntary discharge, etc.).  I suppose it could in the sense that touching the holy while in a state of impurity is disobeying God's law.  Moreover, is the sanctuary defiled until the person with the skin disease gets better and offers his sin offering?  Is the sick person essentially holding the sanctuary hostage?  I don't think so.  The sanctuary is thoroughly cleaned of impurity once a year, on the Day of Atonement (Leviticus 16), which tells me that it can still be used even when it has some defilement (though, of course, the defilement can't get too out of control, for then God would leave, and thus there is the Day of Atonement and little cleansings that occur throughout the year).

Regarding Milgrom's comments on the burnt offering and the grain offering, it would be nice to see more evidence that these offerings atoned for neglecting positive commandments or sinful thoughts.