The completely nonsensical distinction between "Commercial" and "Doujin/Indie" (which extends beyond this issue, doujin-published original soundtracks should technically also be set to Commercial lmao) has been discussed and brought up repeatedly over nearly decade at this point, and nothing's been done about it so far ¯\_(ツ)_/¯
Prior art:
this thread that specifically concerns that field, and
this thread starting at post 81
FWIW my position is still that all fan arrangement albums should be classified the same way (whether that's as Doujin/Indie or with a new mechanism) so they can easily be grouped/filtered/etc., and if we care about documenting whether something is licensed or not, then we should have something explicitly for that instead of overloading Release Type.