Cabin RoC
I am not familiar with the 73 but have many hours on the 75. I have had two occasions when, due to freezing slush, the outflow valve stuck, thus cutting out the auto pressurization. I was fully aware of what had happened even before all the various warnings manifested themselves. Ears can tell a story very quickly.
Were the 73’s pressurization not set, what would have been the cabin rate of climb and would it not have been apparent even before 1,000ft, let alone 10 or 20?