We’re talking about the purpose of squirrels heating up their own tails. Rattlesnake tails are irrelevant.

This has no clear connection to the heating up of a tail and whether it’s related to repelling rattlesnakes.

This strengthens the hypothesis by making it more plausible. The heating in a squirrel’s tail seems to make the rattlesnake feel more threatened, which is what we’d expect if the heat played a role in repelling snakes.

The argument is about the role of a heated tail in repelling rattlesnakes. Other predators don’t strengthen the connection between a heated tail and repelling rattlesnakes.

We’re talking about the effect of a squirrel’s heated tail on rattlesnakes. Whether squirrels can detect heat doesn’t matter, because we know that rattlesnakes can detect heat.