Let me first say - I think you are correct
but - I also don't think that is the only explanation. One other I think reasonably likely possibility is they are hedging. The law gives the POTUS authority to delay enforcement for some additional months if he finds there is 'progress' being made toward divestment.
Progress - is one of those squishy bits of language that can mean anything anyone wants it to mean. TikTok knows they are popular with the Biden voter, and they know an election is coming. Even thought he initial drop dead date is after the election, there isn't anything to say Biden can't announce they are being given the extension early. They might want to secure the extra time by threatening to take their ball and go home. There is not grantee they will be able to get an injunction or stay while they fight this in court, or they might simply want to secure a few extra months to see home many young Americans they can convince to become transexuals.