Impossible to vary square wave FREQUENCY output based on a PWM input?

Since it is a signal from the RC controller, so it a servo or ESC signal.

The servo signal is basically a 20ms period, so it's 50Hz, but as the OP says, it still works at 60Hz.

Also, these HIGH signals fluctuate in the range of approximately 500us to 2500us, which represents the minimum to maximum of the signal.
This signal is correctly "PWM", but few people express it as a percentage of the duty cycle.