I think the 1000ft to go call from pm is to bring awareness to the pf that he/she is approaching the assigned level/altitude.. If I am pilot flying and the pm forgets the 1000ft to go call, and I notice it, I don’t call it because I am already aware, and come on a cockpit is only so big of course i can see if the pm is incapacitated or just busy with paperwork or picking his nose.. of course if he misses every single 1000ft to go then there is something wrong, but missing one or two calls here and there because you are busy with something else is normal!