Rob is right, the rule was put in place because the range has had a lot of problems with irresponsible shooters doing mag dumps (not saying this is what happened here) and tearing up target backers, putting rounds into the overhead baffles, etc. A new hand crank target retrieval system was put in place on the handgun range but had to be removed because people were shooting it up so bad they were destroying it. Frankly, the amount of holes in the baffles is scary. I hate to think what was happening before the baffles were in place. The rule was written in an attempt to still allow some limited rapid fire practice while discouraging people from just spraying without aiming. It's unfortunate, but frankly the alternative was to shut the ranges down except when range officers are present.
The baffles on Range #1 (25/50/75 yards) are a pain, but they had to be low enough to prevent unintentional discharges over the berm.