It's at least highly implausible. Why would they engage in pretty uncontroversially illegal deception/fraud if they have so many other legal ways of gaming benchmarks, selling more tokens etc. available to them?
It's like arguing that your bank is scalping you by rounding down interest math on odd days of the month when they can just introduce a perfectly legal bullshit fee or otherwise change their terms to your disadvantage instead.
They wouldn't be breaking any laws at all. It'd be simply tuning their output as they see fit. And that's if you could actually prove it was even intentional, when in reality they have endless plausible deniability of 'oh it was just a technical glitch we've since corrected.'
Banks have far greater transparency and legal requirements. LLM companies are just delivering a black box that they have complete control over. And given the regular 'How's Claude doing this session?' stuff, it's almost certain that they're A-B testing various tweaks on a per session basis.
It's like arguing that your bank is scalping you by rounding down interest math on odd days of the month when they can just introduce a perfectly legal bullshit fee or otherwise change their terms to your disadvantage instead.