When the security person at Best Buy stops you to check if your receipt matches what's in your cart when you head out, they're not accusing you of theft.
That's not even remotely what happened here though.
When they stop you, say "you stole that", ignore that your receipt says you paid, kick you out of the store, and stop you from coming back, they are pretty clearly accusing you of theft.
That's a straightforward translation of what Twitter did.
Whatever 'translation' you choose, none of it comes anywhere close to accusation of a crime. It's pretty plain from reading the message and the policy. You have to lean pretty far into bombast to turn it into that. Which, if that's how you choose, to read it, fair enough but it has no basis in any of Twitter's actual communication with this user.
If I say "you distribute revenge porn", I'm accusing you of a crime. There's no ambiguity there. Revenge porn is a criminal act nearly everywhere. In some states and some situations, it's even a felony, which is a significant step up in severity.
I haven't informed your local authorities that you do this. But that doesn't have any affect on whether or not I am accusing you.
Twitter has unambiguously made the claim that they are tweeting revenge porn. Twitter has clearly stated that doing so is the reason their account is banned. They're accusing them of a crime.
It's not bombastic or stretching, it's the literal description of what Twitter (via their bot and their review process) is doing.
Twitter doesn't say that, it's, again, pretty clearly spelled out in the policy. The leap from 'our system thinks this looks like revenge porn' to 'you are accused of a crime' doesn't seem to be based on anything beyond umbrage and repetition. Neither of these things make it true, though.
If the system went from "our system thinks this looks like revenge porn" to "we are sending you a warning in case you are, verify that you are not doing it or change your actions immediately. you may be banned on review if it appears you did" I think you might be right.
But that's not happening. It goes from "our system thinks this looks like revenge porn" to "you are banned". And even "we double checked, you are banned". If Best Buy said "your actions seem similar to thieves" and kicked you out and banned you while quoting theft laws, without checking if you had stolen something, yes. I would say they were accusing you of theft, because they are acting as if you did. Actions can accuse as well.
The account was suspended and, again, the policy, which you should read, makes it pretty clear that you can be suspended for Twitter being wrong about your post. It takes a lot of implicit extrapolations ('revenge porn', a term they don't use, 'banned', a thing they don't actually do in those cases, etc) to get to 'accused of a crime'. And they aren't in the thing.
