The incentives are definitely there, but even CEOs and VCs know that if they cheat the tests just to get more investment, they're only cheating themselves. No one is liquidating within the next 5 years so either they end up getting caught and lose everything or they spent all this energy trying to cheat while having a subpar model which results in them losing to competitors who actually invested in good technology.
Having a higher valuation could help with attracting better talent or more funding to invest in GPUs and actual model improvements but I don't think that outweighs the risks unless you're a tiny startup with nothing to show (but then you wouldn't have the money to bribe anyone).
Theranos didn't have 10 different competitors doing the exact same thing. A new AI model which scores better on a random metric isn't going to suddenly make them the top model that everyone uses unless they're actually good. So while Theranos cheating would help put them in stores like CVS, an AI company cheating would just mean that they make a few sales before everyone realizes that their model is actually pretty bad compared to all the competitors.
Having a higher valuation could help with attracting better talent or more funding to invest in GPUs and actual model improvements but I don't think that outweighs the risks unless you're a tiny startup with nothing to show (but then you wouldn't have the money to bribe anyone).