The thing is, who cares? If he used weights then yay, good for him. If he didn't, who cares? It means nothing for or against weights. The argument is entirely pointless.
Well yeah, most boxing trainers didn't/don't really know what they're doing in terms of conditioning/weight loss anyway. The methods used by most are often considered inefficient now.
It's funny, if a boxer uses weights in his training and he loses a fight, he didn't lose because he got knocked the **** out, he lost because he used weights in his training. Always a good excuse to fall back on I suppose.
Likewise when you critique fighters for bad training , ...they won all those titles in spite of incorrect training, whats the difference ?
The difference is that people don't attribute the 'bad' routine as solely responsible for the success of a boxer, but they're happy to say a weighted routine is responsible for their failures. plus, it will almost always serve you better to have extreme fitness and low strength than extreme strength and low fitness.