Sorry, but that bolded bit, is hooey! Popular hooey, from folks that really have no experiences actually shooting small fast bullets, but still hooey.
FWIW, a decent sized Mule deer doe, .223, 50 Grains, at very near that speed, in the ribs. She took exactly two steps and craterd in. I recovered almost 40 grains of that bullet, in pieces, up against the far side leg bone. Innards (heart, lungs) were jello.
My brother took a very nice Mulie buck with the same rifle and loads, and a guest here at our Farm took a nice doe as well, with another .223, using basic commercial loads.
As one of the guys here pointed out a while back, the big argument when he was up North, was usually between the old guys that thought a .22 Hornet was all you needed for cariboo, and the younger fellas that thought you needed at least a .222.
I'll not claim that a .223 is the best all round deer cartridge, for all people, but in capable hands, it's a capable killer. And that 'disintegrate on the hide of a deer', is hooey!