... 5 powder stages from lowest grain recommended to highest grain recommended...
You have misunderstood the use of the data. You are supposed to start at the lowest grain weight listed for that bullet, and test in increments until you either get signs of high pressure
or, until you reach the highest grain weight listed. In your case, you did not stop at beginning pressure signs
(or your increments were too large...for a pistol use .2 (that is two tenths of a grain)), until you find your accurate load, or high pressure signs begin
So, of course it is an indication of high pressure.