There was a minor ordering issue in EXOT4, where truth algorithms were being added to the derivation after the main sequence, which needed some of those algorithms. This MR just swaps the order, and thus fixes the derivation. There's quite a bit of other clean up that would be possible in this derivation code, but I'll leave that to the contact.
Resolves the discussion at the end of !35120 (merged) . FYI @boeriu