Some people consider failure to be "completely unusable" - others say "if it doesn't repeatably track or return to zero - it's not working as it should - that's failure"
First group - says "my car burns oil, the passenger door only opens from the outside and there's a weird shimmy above 55mph but I get where I'm going and have been for 2 years!"
2nd groups says "it may work but it's still a chunk of chitt, this is better over here...."
For the person who buys a rifle to hunt deer with, a scope behaving imprecisely during zero is of no consequence. That shooter will get it zeroed and never dick with it again. That's not a failure, since the scope serves its purpose of allowing the shooter to kill deer. Then an internet blowhard comes along and insists that scope is a failure despite the fact that it does exactly what the shooter wants it to do.
