He thought his strength weakened but his internal deepened, but that doesn't necessarily mean one canceled each other out. He could have gotten stronger internally more than he got weaker physically, which I think is the case.
And in PJ's quote, H7G thought he advanced greatly without the caveat that he got weaker physically. It would be a bit misleading of JY not to state that since any reader reading that would just take it for what it's worth and believe he got stronger absolutely. And while I don't think HYS got weaker physically and H7G did not, I think that it implies their overall fighting ability did get stronger.