60rpm is usually the value where you start to lose form so it is a good target.I did some low-cadence drills on the trainer today. But I am limited by my gearing and my trainer's resistance curve, I can only get down to 60 rpm and hit my power targets. But it felt good anyway (3 x 12 minutes of sweet spot at 85 % FTP, a really easy workout).
As strength work I try to do them in muscular endurance zone 3.
Like you say, not so demanding. I like to do them after higher intensity intervals to "finish the legs off".