True. Also I think Tunney and his team would be wise to have opted for 10 or 12 rounds. A lot of it is down to how long Tunney can keep circling and jabbing. Rocky would put serious pressure on him. Tunney UD 10. Tunney SD or MD 12. Over 15 he’s in danger of running out of gas and getting corned for a stoppage loss.
Not necessarily non-favoring Marciano -- though I don't see Tunney as a long-shot -- but I think the 'doesn't hit hard enough to hold 'X' off' might be overlooking that Tunney was pretty good at hitting an opponent coming in and a good counter-puncher. In those instances, Tunney was in essence hitting an opponent with some of his (opponents) own strength. I'm not saying that makes Tunney a thunder-fist, but I do suspect his punches often landed with somewhat more crack than they seemed to be thrown.
The only way for Tunney to win a 15-round fight is to knock out Rocky Marciano. If he tried to be smart, and box defensively; that would not be wise. I just don't think Tunney can win this fight on points; in fact he cannot win at all.