It's mainly for IRShell 3.9 compatibility, since any POPS version at or below 3.80 seems to works under it.
I don't know where to go from taking the 3.80 m33 v2 popsloader.prx, stripping the bytes up to offset 0x00150, renaming the now smaller file as a .gz, and decompressing that new file.
What prompted me to do that is the one slight graphical glitch in Vagrant Story, where savegame icons within that game have inverted colors in older POPS versions, but look fine in 3.90. It lead to a futile quest to make POPS 3.90 work under IRShell (Which I could've sworn happened once), but now just having a 3.80 choice seems like the next best solution (though that doesn't fix the glitch, it might make more games compatible with IRShell, without having to use CFW 3.80 M33-5).