I wouldn't get to caught up on tips. Tips I could only see being used for as a means to create a certain band-wagon effect such that when everyone sees everyone else tipping then whatever they're tipping for must be worth the tip. Meanwhile likes are free and really do boost you in the OF algorithm.
If I can make dozens of accounts so can many of the "top" earning girls who can also basically like themselves to boost their page to the top.
Also this isn't anything new. Most of these girls also employ bots to artificially boost their ratings and views on other social platforms such as twitch, etc. If you think some of these content creators like Jenna Lynn Meowri that get 5000-10000 likes per day per Onlyfans post, don't use an artificial means to boost their account/likes then you're delusional.
It's not that hard to imagine that some of these same girls would then go so far as to tip themselves in exchange for a little tax money or do whatever they need to boost their page.