"The PSP rules also state that only a maximum of 3 shots per trigger pull can be fired."
If they can police that, they can police 1 shot per trigger pull.
But I figure it actually means that the pulls to start and keep ramping up will be raised to 4.4 pulls per second, instead of 3.x it is now.
So its actually two changes. One to lower ROF, the other to raise (very slightly) the difficulty of ramping.