while i'm obviously sure it's a bluff, pulling out instead of selling would be the clearest admittance that tiktok is (or at that point: was) not about the profit, but about Chinese influence in the US. the message being "we rather leave a hudred billion dollars on the table than give away our surveillance technology to some US company."
There are valid commercial reasons not to go through a forced sale with a ticking time limit, which will inevitably carry a steeply discounted price. Rather than getting robbed, it makes sense to hang on to the company and take profits from the rest of the world.