They hope to significantly reduce the pressure on politicians to take a close look at their App store practices by significantly reducing the absolute number of developers suffering the full impact whilst taking the minimum possible hit to their revenue. This has nothing to do with “doing the right thing” or “accelerating innovation” and everything to do with limiting the number of outraged letters to senators from devs, the number of newspaper interviews with prominent indie developers & so on.
Indie devs have an outsize PR impact relative to their revenue contribution, so buy them off with a smaller revenue tax that delivers outsize returns if it prevents the 30% house rake on the majority of Apple’s App Store income coming under scrutiny.
Apple / Google’s 30% take is the anti-competitive elephant in the room here, not a few crumbs thrown to small developers.