Overall compression doesn't usually just tapper off unless the rings/cyl walls become scored, worn with mileage. Despite the "200 psi" spec, most engines won't really read that high when checked. It also depends on the tester/guage itself, how many cranks, engine temp, etc. 160psi-ish is OK BUT the "20 psi" difference might be a concern as a healthy engine should all be very close. I'd also question reading by a "junkyard tech" (hardly a tech really) as that could just be BS, like the stories that almost all used junkyard engines/trannies magically have "30K miles" on them, a very common mileage for engines when asked and has been for decades. What, everyone totals a car with 30K miles?

With junkyards, unless you see the car with its odometer yourself, you never really know what you're getting.