Here is a quadrant analsys from a pro rider (500w Z5 ). This is in Italian (I added some English over it) but you can see there is always a relationship between force and rpm to produce power. This left top quadrant is something that most non-pro riders don’t train. They might do sprints of short duration high force that are briefly in this quadrant but not sustained (strength/endurance) like low RPM can produce.
If you do VO2max or HIIT workouts they still don’t produce enough force unless you do around 55-60 RPM.
SFR is best for indoors unless you have a long steady climb around 5-8% grade without a lot of interuptions. You will find our SFR workouts starting rather mild (4 X 1min intervals) but as you build up you will see they are definitly causing positive adaptions.