Depends how hard you normally have your tires. I was pumping mine to about 120 psi before I was advised not to but that's to some degree down to personal preference. And talking of degrees, change in temperature has an effect too.
Certainly you need endurance, and a short session doesn't (on its own) give that. But does that mean that if you do a short session it should be hard? Not necessarily. Workouts fit into a plan, and if you need an easier workout to recover then a short easy bike is better than nothing.
The biggest mistake is trying to fit intensity and endurance into every week for all three sports.... You just can't do that many hard sessions.