>other owners say it runs fine without coolant, oil, etc - just keeps plugging along.

This is called lying. They are lying.

Depends on what you are asking of the engine. An engine at red line but under no load doesn't generate that much heat, and so can get by with no coolant, and run for a long time on just the oil film left after draining the oil. This is really bad for the engine and it will wear out much faster - but it will run for a surprisingly long time.

	▲	throwawaylaptop 2 hours ago \| parent \| next [-]
		These are random little examples that might work in theory. Sure, a car can idle for an hour without coolant probably in the winter, possibly. I can't be driven on the street in any meaningful way anywhere but a Minnesota winter. If you can't drive to work 20 miles away in 75 degree weather without coolant, than no a car can't run without coolant. And no it can't run without oil in any meaningful way on the street for more than maybe 15 minutes.. so again, no Honda Toyotas are no built so well that they run without oil.
	▲	jfindper 4 hours ago \| parent \| prev [-]
		"This is really bad for the engine and it will wear out much faster" is significantly different than "runs fine [...] just keeps plugging along". But yeah, you can limp along without the essential fluids for a bit.