Hi guys, can i pick your brains?

Basically, my beloved Scudo engine messed up. Overlooked worn serp belt got pulled into timing belt when running and caused all sorts of problems. Engine is done. Got another engine from a scrappy that was sent to my mechanic to be fitted but he put a breaker bar on the crankshaft pully and there is zero resistance. he said the engine is no good....no compression. Breaker insists it's definitely a running engine and said to fit it and see. Mechanic said he doesn't want to waste my time and money by fitting an engine that's not gonna run. I know heehaw about engines so would there be noticeable compression or not? Mechanic says there should be and i've felt compression before in a different engine. Trying to slug it out with the breaker.

Ask the mechanic to call the breakers.