Personal Pet Peeve ! The receptacle should match the the rated voltage current and current of the breaker along the with appropriate wire gauge. 120VAC @ 20A should have a 5-20R (Yes, I know a 5-15P will work on a 5-20R and that most (all?) 5-15R will handle 20A !). Same should be true for...
I think a big part of the issue is the length of the wire (and therefor the voltage drop) from the breaker panel, through the receptacle and plug to the motor windings.
Most houses built between the 1950s and 1990s are wired for 15A. (I'll bet it is still true today except for where code...
When I vacation "up north", the town has a "Gil-Roy's Got it" hardware store. Not big, but they do have it ! Chain saws, hunting and fishing gear, kitchen gadgets, plumbing, electrical ... It is fun just wandering through it !
That is a really STUPID statement ! If that was true and the NEMA 5-15P that it came with was connected to a 15A breaker, that breaker would trip before 5 minutes !
NO ! Technically it wants a a 120V- 15A circuit !
Will it work. YES ! Is it "code compliant" ? Probably not.
You can overload/burn out the motor because that adapter comes with a 20A breaker !
Years ago, wood block floors were common in factories. Compacted sand and 4x4 or 6x6 blocks, grain up . They were cheap and durable. Water and oil passed straight into the sand. Easy to repair.