I just took a course in control. Perhaps it has to do with the gain margin and phase margin? Each of those margins is a measure of stability. For an oscillator you want marginal stability. The poles should be located on the imaginary axis for sustained oscillation without growth or decay. The phase margin should be exactly zero degrees. The gain margin should be 1 or 0dB. Look up the Nyquist diagram on wikipedia for more information. I am guessing it has something to do with that. Not sure though.
Typically for a non-linear bistable multivibrator you don't worry about loop gain and phase margin as such. That's generally used for linear feedback systems. You just design the circuit to have enough positive feedback to flip the state at the end of each half-cycle.