Actually, Vrelnir doesn't merge anything, contributors set up git mergers which either LolipopScythe or PurityGuy handles (I wanna say lolipop, but not positive). Should be easy enough to verify, but if absolutly needed I can dig through old discord pm's with Vrelnir and post something (for some strange reason many people just don't trust random folks on forums. Go figure)
As for the the "huge list of features and content that has no direct crediting to a contributor", here's a full list for the last year (also since 4.0 convieniently). Month/year listed for ease of confirming.
3/24 - For 4.6, there's 1 (sensitivity shown in characteristics)
12/23 - For 4.5, there were 0
12/23 - For 4.4, there were 2 (temple quest to the island, and a shortcut to island.)
10/23 - For 4.3, there were 3 (another temple trial, 2 additional weapons, and a feat.)
10/23 - For 4.2, there were 3 (a loft upgrade, a bad end, and some feats)
6/23 - For 4.1, there was 1 (added a condom machine)
4/23 - For 4.0, there were a bunch, as there should be for a major upgrade.
Possible I missed something, only skimmed them since I'm not wasting much time on this, but in the 11 months since the 4.0 release, the only significant things Vrelnir's left uncredited are 2 temple things, a loft upgrade, and a bad end.
Note: Didn't go though the subversions, they're mostly bugfixes and Vrelnir hasn't done those for years