I don't think that was violated, no. He literally has defense lawyers currently presenting a case and in the house they're really just supposed to collect evidence. In that regard, they attempted to and their subpeonas were defied. That's not how it's supposed to work.

Trump isn't supposed to present a defense to the house tho. That's pretrail fluff. His defense is supposed to be in senate which has absolutely happened.

Trumps defense now has an opportunity to address those witnesses, and is choosing to push for them not to speak, and for the trial to end hastily.