No, this is something different. The law allows a 90-day reprieve only if significant effort has been expended towards selling TikTok. But ByteDance hasn't made any effort at all. Trump is instead trying to prevent the Justice Department from enforcing the law. But the penalties -- and they are very large -- for violating the law can be enforced any time up to 5 years after the violation; that is, after Trump has left office. So his action may not have any effect.
Oh it'll have an effect: the benefit of a law you could enforce but don't is that it sends an unambiguous message about the quid-pro-quo which is expected.
Yeah, but would Verizon (let's say) let TikTok on its servers given that they'll be fined for it retroactively (in 4 years) regardless of Trump's order now? And it's a big fine.