Disowning current tariffs doesn’t mean they’ll go away, either, though.

Tariffs are easy to put in place, but hard to roll back. You can put then in place on a whim, basically, but then the target country will retaliate with their own. As a result, removing them requires diplomatic negotiation to make sure the removal is bilateral. That’s not easy to do during times of icy relations like China and we currently have.