That is correct. Taylor has some stamina problem, most likely psychologically related, that he cant seem to get past. Weve seen fighters in the past with the same problems. Bruno, Morrison, Briggs, Wlad K. to name a few.
Simply not enough road work, nothing wrong with maxing out bag or pad work until you can't breath either. Plus too much speed work/weights work will see a fighter punching themselves out, they'll be more explosive/faster/more powerful but that comes at the price of using up too much energy in the early going Taylor also has problems on the inside too though.