[Retr0id]

Only because TLS never tried to be metadata-resistant in that way.

For example, Noise protocol + Elligator + constant bandwidth, is indistinguishable.

[andrewflnr]

You do have to try, though, is the point. It's not automatic just because the output of the cipher itself is cryptographically random. And when you do try, the lack of metadata will itself be a clue as to the software generating it.