Oh yeah that’s fair. Basically the ESC switches power on and off to the motors in very fast cycles. At 20% speed, it pushes 85A into the motor for ~20% of each cycle. This “on time per cycle” is the duty cycle. [1] [2]
The ESC has large capacitors that average out the current draw across cycles, so instead of seeing very quick spikes of 85 the battery sees an average of (85)X(0.2)=17A.
Biiiig simplification there, but there’s a thread on it with a few explanations
[1] The reason the motor isn't jerky when you're turning the power on and off all the time is:- It’s got a lot of mass and rotational energy, so it’s just really hard to change its speed with a pulse that’s 0.00001s long
- It is an inductor, which stores and releases energy in its magnetic field. If you don’t like electronics, this functions similarly to intertia in a spinning mass.
[2] I’m using 85A assuming full throttle. The same maths applies at any other value: ie half throttle at 60% speed would roughly look like (42.5A)X(0.6)=25.5A