When someone has a percentage of a games revenue, any Robux earned from avatar shop items commission within the game will go to group funds instead of directly to the user.
Despite having a percentage of the game revenue or group revenue, you will only receive a share of dev product / gamepass revenue. I noticed this as a game I have a percentage in has avatar shop items commission as a primary revenue source and all of that revenue goes straight to group funds.
Donation games like PLS DONATE 💸 - Roblox make most of their profit from sales commissions on gamepasses and avatar items, and this being intended behavior renders the % payout feature useless for these kinds of games/groups. I was added to the payouts tab of a similar game with a certain percentage, and only months later did I realize I was only getting 10% of the funds I should have been because of this issue. At the very least, there should be clear warnings/documentation on how this behavior is not supported as of yet.