Refining his abilities makes him stronger. There are the books themselves that show Harry working out to be more physically stronger....jogging...training in martial arts with Murphy...etc....
Since you don't include the link to the woj...it could be outdated, you know.
Still...I think what is actually shown in the story should supercede woj...since writers sometimes forget what they've written.
sorry i don't know howto do a link
but he is a copy and paste
2011 Bitten by Books Q&A
Now that Harry has used magic in this book without and tailismans, will he be a stronger/more adept wizard with his magic in the next book?”
Harry really hasn’t gotten all that much stronger since the series started. He’s gotten more efficient, more skilled, and smarter, and inasmuch as that makes him more powerful, that will continue. I mean, what doesn’t kill you only makes you stronger…
Oh wait.
and your right physicaly he has imporved