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Yeah, my coach has me doing these at the moment for 1 min at 50-60rpm. It's not really to build strength - it's pretty much designed to aid high torque seated accelerations on large gears (sprinting, basically). I guess it would have benefits any racing where you need to do seated accelerations...
The efforts are pretty unpleasant at the time, but don't leave me in a mess the next day - unlike high load sessions at the gym.
Tl;dr: If you want to build strength - get in the gym.
It's not going to build any strength. Think about it logically.
You will get used to producing power at a higher torque. Which there are benefits too. I do think there are benefits to low cadence work. But not specifically in directly producing more power.