See Rule 6.19: Timed Events, and Rule 16.2: Resource Usage.
6.19 says Player Power must play at least one card to roll to end a Timed Event.
Rule 16.2 says play of "+" Resource may be in lieu of card, and says in its last example that merely trading Resource to draw card is a card play.
It does not seem quite fair to minimize MUD effects this way, but the rules seem to say it is legal.
It is perfectly legal. I look at this way, you're still getting the benefit of delaying you're opponent's movement.