I Believe that Short-cuts on MANY kits are giving Pistons More room to Not bind so that the cylinders Don't need to be torque-plated and $$$$$ saved in machining time...
Not un-common to hear the Slap as 6 thous clearances are NOT uncommon today (bad Kits)...
Buyer Beware is the best advice..
Harley comes "Generic Size" on their stock replacement cylinders sent out (at least to Me long ago) going 95" on my 2000 FXDS, new cylds. giving More than Needed clearances..
I bought the cylinders and HD
SE pistons separate. Only to have to Exchange them go .005 Oversize on New pistons and torque-plate Hone in the over sized pistons by a few thous to FIT the Cylinders Properly HD
I would of sounded like My 441 BSA using their clearances.
That was Long ago.. And I don't Doubt it is still in the many KITS of today.(loose fits)
I have Adjusted my thinking long ago,,,, BUILD your Own Kits to fit Properly and you will save $$ in a long run.