> he could have offered private and legally binding statements
No, he couldn't? It's not even clear he'll be able to do anything with an executive order when he is sworn in, but President elects certainly can't.
I don't know why you think he couldn't. A legally binding statement of intent to offer TikTok the 90-day window and work out a "deal" once in office would be more than sufficient justification for the heads of the various companies involved to ease enforcement until things become more resolved.
> A legally binding statement of intent to offer TikTok the 90-day window and work out a "deal" once in office
Would not be legally binding. The President cannot unilaterally bind the U.S., and he is free to make and break statements of intent.