There are many subjects being discussed here that appear to be ripe for testing on "Mythbusters"...
Let's light the touchpaper with an extract from the O-320 powered PA18-150 POH (SuperCub):
"When the engine is cold, prime three to five strokes after turning the fuel valve to the proper tank. Push mixture control to full rich, carburetor heat off, and open throttle about one-eighth of an inch or until the intake of air at the carburetor can be heard when
the engine is pulled through by hand. Engine should be pulled through at least four times."
Gosh!
There are many different opinions in aviation surrounding the serviceability checking and operation of aircraft - some of them might even be correct (excluding the manufacturers', of course
).
I'm not going to offer any opinions, other than the suggestion that a bit of critical thinking goes a long way when assessing some of the 'lore' that gets quoted sometimes, and to treat any powerplant as something that will burst into life as soon as you're within injury range.