I’d guess that’s one reason for taking this step – the step of drafting a withdrawal memo, I mean. It’s “safe” because it doesn’t actually result in withdrawal. It’s like passing legislation repealing the ACA over and over while Obama is POTUS.
I’m not suggesting there’s no impact. There could be a highly negative impact if our trade partners become motivated to abandon us and look for more reliable counterparties. But for Trump, that’s presumably irrelevant. What would matter to him is whether he can claim a checkmark-victory and whether he can blame trade-related bumpiness on his political rivals.