It looks like this is only for preparation of User Copper List, which is never executed by itself, but is being merged with the other Copper Lists into One Big Ugly Copper List and that one is finally executed, so only that one has to be in CHIP.
Now Piru says I'm right.
You're right.
Anyone interested in learning how this all works should read intuition.library/RethinkDisplay and graphics.library/MrgCop and related autodocs.
Also, this merging might explain why there are additional limitations to what you can do in the user copper list.