I don't know about this. Paying attention to how your anxiety feels is a powerful way of noticing that it is just an experience like all other experience and there is a great freedom in realizing that you are not the anxiety, you are merely experiencing anxiety.

I don't think I've ever gotten a panic attack from paying attention to anxiety.

It's an interesting point, I experience it the same way. Disconnecting the anxiety from the topic you are relating it to is a very powerful tool. If I am feeling anxious, it is not necessarily because of the thing I was thinking about.

Sometimes I started feeling anxious first and then retroactively assigned the topic to it.

In the case that I am ruminating over something that does actually worry me, I can get into a spiral of reinforcing thoughts that increase my anxiety.

Paying attention to the feeling, not the thoughts, lets me break the spiral and attempt to free my thoughts. The feeling can linger for some time though, given its a chemical process to flush it all out from the body. During that period it's more likely I might end up thinking about the topic again so it's precarious still.