My best guess is there needs to be a real SIM at the very least, so that the requests come from legitimately different and randomly distributed IPs. So you nee

My best guess is there needs to be a real SIM at the very least, so that the requests come from legitimately different and randomly distributed IPs. So you need a system that can virtualize all that, but still go through separate SIMs. The cost of developing something like this probably doesn't outweigh the "ease" of just faking it with real phones. (On top of this I have my doubts about how much "tens of thousands of phones" costs for someone who doesn't care about grey areas)