I'm uncut also , still, but recently tied (searched a way how to remove my frenulum) .
One reason was aesthetics but this came after i had the similar problem you had...
I started getting very tight stretching feeling from the frenulum, especially when penis got so hard it went to new length ...
Especially those max 10 hardness, i got so limiting very uncomfortable feeling from frenulum.
When pumping even further than normal max hardness was almost out of question...
And the frenulum didn't want to adapt whatever how much lube i used over the years...
Finally one day decided okay it has to go...
i'm 90% frenulum free now, last 10% to go still.
Now after this , i'm 100% sure frenulum DOES inhibit the length growth...no question about it,
Frenulum will hold back how hard you could get, think about this,
if you would get too hard you would just rip the frenulum...
When i got rid my frenulum i got instantly 0.2-0.3 inch on length gain on max hardness vs before , and i thought i had 10 out 10 hardness before...
...Nope...
After decades of life ....
I was so surprised that frenulum does inhibit length growth ...
Good luck
I wouldn't want to debate on this, but now having no frenulum and from personal experience,
I even believe that having frenulum removed before puberty would increase the adult penis length,
Cannot prove this,
but my logic and experience is this that after getting the max hardness, what is the first this that holds back further growth --- frenulum (besides the max blood supply)