The
8501 has no NMI# pin:
There is no wire bonded to the NMI# pad of the chip.
So we can't just observe what effect a glitch in the power supply might have to the NMI# circuitry of the 8501.
Unfortunately nobody in this forum seems to have an academic degree in semiconductor physics,
so debating about what the designers did there and why, which effect it exactly might have etc.,
only would be speculative without leading us to a useful result.
Would suggest to buy an 8501 for $70 at ebay, then to inject pulses into the power supply and to see what happens.
But I won't do that.
Actually, the purpose of this dissection was to gather enough info about the 8501 innards for building a FPGA based 8501 plug_in replacement,
because it became increasingly difficult to buy (used) 8501 chips as spare parts, and because the ebay prices for said chips went through the roof...