OP already mentioned that it adds additional hurdles for possible future tech giants to have to cross on their quest.
It's akin to a Great Filter, if such an analogy helps. If Meta's open models make a company's closed models uneconomical for others to consume, then the business case for those models is compromised and the odds of them growing to a size where they can compete with Meta in other ways is mitigated a bit.
I think we should not underestimate the strategic talent acquisition value as well. Many top-tier AI engineers may appreciate the openness and choose to join meta, which could be very valuable in the long run.
Web standards are probably the last thing Google cares about with Chrome. Much more important is being the default search engine and making sure data collection isn't interrupted by a potential privacy minded browser.
It's akin to a Great Filter, if such an analogy helps. If Meta's open models make a company's closed models uneconomical for others to consume, then the business case for those models is compromised and the odds of them growing to a size where they can compete with Meta in other ways is mitigated a bit.