I don't think you understand. At all.

There are no known caps in the game. Only walls. Once you climb the wall, you get the bonus.

On top of that, the only testing he did was at BASE Dex, +15 DEX, and +30 DEX. Given that STR has walls out past +30 STR, I am pretty damn confident that DEX does as well. Only a fool would take extremely limited incomplete data and use that as his defacto reasoning for X.

Seriously guy. Common Sense.