There is one local poster who continually claims that it is possible to get more than 3 FP+ in a day.
If that is the case, I don't see how it would not be more widely discussed by dozens (hundreds?) of guests who could simply try it at any park, any day, day after day. The boards should be filled with firsthand reports of guests getting additional FP+ if that were true.
So far, the consistent reports are that attraction FP+ totals remain at 3 per day.
That's what I tend to believe until a majority of new reports come along to confirm otherwise.
And, yes, things can CHANGE at any time regarding anything.