Just an oversight, a common one. A great many don't watch enough Liston to realize what a solid technical beast he is. He's famous as a puncher, and a heavyweight one at that and heavyweight punchers aren't usually an overly skillful lot. I've seen a helluva lot of people gain insight and respect for Sonny's skills over the years once they've looked at him in a deeper capacity. There's also a minority who may as well be watching ducks waddle or simply just want to hate, or even both. We all know a couple of those. Have a look at Tin Ribs post a page back. He's at least as good as anyone I've ever seen when it comes to describing fighters, fights and how he thinks fantasy matches might be fought. When a bloke like that heaps such high praise you sit up and take notice.
I think Liston should be on here too. There is a lot to like about Sonny’s punch placement, his ability to switch from long to short range mid combination without losing form. It’s probably overshadowed by his power.