I take it you don't play either card or chess very much.
When the other guy is leading with a feint, you don't want to follow because he has something else in store. Sometimes called an ambush.
Ms Rice has already testified in private, to change that now would be to hand the bad guys an ace, or in this instance, leave the Queen at risk.
PS....NOTHING is going to "prevent the media and the dems from using her lack of open testimony as proof..." of any damn thing they agree to!
I agree with you in regards to a feint, but I don't believe the dems have one in this case. If the administration is fearful of this perhaps they can find a way to work around it. If not so be it (that's called not ceding the higher ground without good reason).
Frankly, using poker parlance, I think it's a bluff.