A constant off time controller and a hysteretic are closely related.
My first controllers were "voltage" mode. The controller only watched the output voltage. If the input voltage jumped 2X the error amp did nothing until the output voltage was wrong. Then the error amp started to slowly walk over to a new duty cycle.
Years later when the UC3842 came out, it watched the current on every stroke. A 2x jump in input voltage caused a instant change in duty cycle with out the error amp needing to respond. (very nice) It also had good short circuit protection. The on-time is set by (InVoltage * Time).
With hysteretic we have (InVoltage * Time) and (OutVoltage * Time). Because Vout is constant, a constant off time controller is (approximately) the same thing.
Years ago, a controller that varied duty cycle by errors in output voltage was all we had. (better than linear)
A controller that directly responded to 'input power' (with out the error amp) was a major jump.
I have built controllers that watch output current and respond. (without the error amp)
Now there is more than duty cycle. (on time, off tine, frequency, phase, etc)