Which is exactly the practice that needs to stop.
You and I both know there are far more than 8 ATC controllers that work LGA. Please don't try to assert that there was no way to even have a relief available. (As appears to be the case in this instance.)
Whatever caused the lack of availability that night needs to be urgently addressed. Please don't try to tell me we would have needed to train more ATC controllers to provide even a single relief at that tower last night. We both know how many ATC work LGA so we both know that's not true.
What caused the lack of availability is the well-documented understaffing. Everyone in aviation knows that ATC is understaffed right now, and the reasons for the understaffing are well-understood. To come in and instead say, "well, I'm a mathematician, I'm going to make some simplifying assumptions - the only simplifying assumptions permitted - and do some basic arithmetic to show that there were hundreds of controllers available, clearly the guys responsible for ATC at LaGuardia don't know as much about running an airport safely as me" is beyond silly.