What's that phenomenon where as a child you were told a "fact", internalised it, and lived your life presuming it was true until someone points out how obviously wildly untrue it was that you momentarily question reality?

Because I was today's years old when I realised how ridiculous cutting complete blood flow would be. Thank you (genuinely!)

Maybe a bit, but there would have to be a ton of pressure. Consider the fact we have to use a tourniquet to cut blood flow typically, and those hurt like hell.

Your nerves are responsible for making your muscles move. Blood only keeps them alive, and it takes quite a while for lack of blood to actually matter. A rule for tourniquets in medicine is 4 hours if you want to keep your limb without permanent damage.

A good indicator if blood flow was actually cut off is if your limb is extremely pale (within just 1 or 2 minutes) or later goes blue. But if your nerves are unblocked, you can still move your limb for quite a while even without blood flow. Usually though, if blood is cut off, nerves also are.

Because the nerves are compressed. You move and feel your body via nerves.