Hm, given how many requests Meta and Google disclose annually

I dont think a warrant canary is really useful, it implies “we just got 1!” instead of “we just got an additional pile of 200 secret requests from G-7 national governments, one of which is already trying to incarcerate us for not being so forthcoming about compliance”

Given that you won't know the details of the 1 or 200 requests anyway, I think knowing the difference between 0 and >0 is useful. We do know what 0 means, and anything other than 0 means the platform's got the attention and jurisdiction of outside parties.