What tension? If in-game-time is not a resource that
means anything, then there is no tension. The logical apporach becomes "rest up whenever you have any resources to regain at all", because (re)gaining one resource for no resource cost is a bargain!
It's only "an issue" if stopping to rest and recover resources actually has any cost. If in-game-time is not a resource, then there is no cost and the "5 minute adventuring day" becomes a logical thing to do. That was always exactly its problem - it's the (only) rational approach
as long as in-game-time has no value as a resource. You can pretend that in-game-time matters as much as you like, but as long as resting is "free" it's an irrational way to play the characters. Ask me, IRL, whether I'll take a risk and push on with a hazardous task while tired, hungry and sick or take a rest and recover somewhat, if resting is an available option and there's no real hurry, I'm going to rest
every single time. To do otherwise would be irrational (and not at all sensible!

).
But there is no conflict of priorities, class balance or no class balance, unless recharging is actually something that has a cost. Otherwise the fighter should be fine with resting whenever the wizard is down a spell, and the wizard will rationally be fine with resting whenever the fighter is down a few hps.
As soon as resting has a cost, all of that changes. THEN it becomes a matter of hard choices, conflicting priorities and carefully judged decisions. THAT's why I want it made clear what role and value in-game-time is supposed to have - balance or no balance.