https://bugs.winehq.org/show_bug.cgi?id=47600
--- Comment #4 from Damjan Jovanovic damjan.jov@gmail.com --- (In reply to Austin English from comment #3)
Bug 1490 was about a similar issue, which was closed WONTFIX with the suggestion to manually unset the variable as you did, or use `env -i`.
Thank you, I'll chat to AJ.
There used to be a list of variables that wine treated special (in dlls/kernel32/process.c), but it seems that was removed (didn't try to find when/why): https://www.winehq.org/pipermail/wine-patches/2010-February/085002.html
It's been moved to dlls/ntdll/unix/env.c and seem to rename the variables instead.