The proof without a doubt are in the pictures I posted after your black and white one.
If you think his back didn't improve alot then your entitled to your opinion but I disagree
and I believe the pictures I posted prove it.
I said it did improve but by 1996/97 his back was already thick and wide and comparable to his 1998/2001 in terms of width & thickness although not as dense which doesn't matter because Yates wrote the book on width , thickness , density , depth , and detail
Now just based on this look at the thickness difference , the size difference ( length ) of the traps , infraspinatus & teres , look at how much lower his lats insert near the waist NONE of these change with added size , he added some thickness sure and width okay BIG DEAL Yates wrote the book on it