No Decalogue in J?

One of John Van Seters' main arguments in Life of Moses is that J used Deuteronomy as a source, rather than vice versa. Regarding J's use of Deuteronomy 4-5 in Exodus 19-20, Van Seters argues that J rigidly follows the sequence of events in Deuteronomy 4-5---even though Deuteronomy does not regard those events as chronologically ordered, but rather as Moses' retrospective musings on the past. The result is that J creates a narrative that doesn't always make sense---the Israelites agree to obey what God has already commanded before God has even delivered his commandments---and also that J makes Moses go up and down the mountain a bunch of times---and Van Seters' argument is that J is giving Moses a separate mountain trip for interactions that Deuteronomy says Moses had with God (Deuteronomy 4:10-14).

Van Seters also contends that J replaces God's divine voice in the theophany with a trumpet blast to provide an etiology for the use of the shofar in the cult. Moreover, for Van Seters, J does not present God speaking directly to the people, for J wants to confirm Moses' role as mediator. In J, Moses receives the commandments from God to communicate them to the people. But what were these commandments? I am unclear about whether or not Van Seters includes the Decalogue in his definition of God's commandments in J. On page 276, he says that the Decalogue does not fit into the Yahwist's scheme, but, on page 279, he says that, in J, additional commandments are given at Sinai. But, if there is no Decalogue in J, are those commandments (the Covenant Code) really additional?