I'm guessin' some of the guys here think that if you'd look at just one of the cylinder heads and barrels of the V-Rod, then there is a similarity between the two bikes. They are talking about the motor of each more than they are anything else.
Both are water-cooled, both have cam-end "eyes" along the top of the heads right where the "cooling fins" are, AND, the following, which I believe is the CRUCIAL similarity here....there are little or no cooling fins along the somewhat slab-sided (and in my view, which makes the engines somewhat boring looking) cylinder barrels on either of 'em, AND which makes the engine's top end look out of proportion and a little too large compared to where those pistons go up and down, up and down, up and down!
And, ALSO making the engine look more modern and water-cooled...WHICH, once again in my view, makes ANY "Retro-styled" motorcycle...which the T-Bird IS...look, well, a little less "retro", read: AIR-COOLED!!!
(but once again...other than THAT, I LIKE the looks of the T-Bird, especially that blue one, but...once again...yep....IT SHOULD HAVE HAD FINS ALONG THE FRICKEN CYLINDER BARRELS...well, more than those "attempts" at fins there, anyway!!!)