Would these signs really work in a robbery?

Every business, fast food joint, convenience store seems to have these. The height strips alongside the exit door.

The theory is after just having had a loaded gun in your face the minimum wage paid employee will still be such a good company man that he'll have the presence of mind to take a mental note of where the armed robber comes to on the height strip as the exit the building. (Yes, yes, I know they have security video they could go over but that doesn't accommodate my sarcasm so I was going to leave that out.)

Not sure if this ever once solved a crime. Nonetheless, if that's the theory, don't they have something wrong? Every one of these I see is just like this one, starting at 4 feet, then 5, then 6. Are they getting a lot of midget robbers?

I'm sorry, little people robbers. I don't want to offend a robber. Are they getting children brandishing .38's? Shouldn't these height strips start at 5 feet, then 5 and a half, then 6 and maybe up to 6 and a half? Although if Vern Troyer knocks off a Wawa then who'll look stupid?

Guess I should just keep my mouth shut.