Going back as far as I can remember ( some thirty five years), the casino craps personnel have been warning players to hit the back wall. Some times I think it is a automatic reaction to any throw that misses the back wall.
I remember one time when I missed the back wall with one die and the dealer in a bored monotone says, "you have to hit the back wall". The stick guy came right back with,"wake up, this guy has been playing for two hours and hasn't missed the back wall till now".
Another time in a downtown casino where I swear the table was only a ten footer, I missed the back wall while try to adjust to the short toss. This older stickman says, "try and hit the back wall sir". After my next toss the stickman whispers to me, "thanks for hitting the back wall".
I wouldn't consider either one of these occurrences "heat".
Heat is when they, the table crew or pit vipers add a remark to the back wall warning, such as, "or you will have to pass the dice". That's the start or real heat.
Most of the time they are just doing their job and have been programed by the suits, If it doesn't pertain to me. I don't worry about it.