[Stuart]

But it wasn’t called that, was it?

Technically, yes it was. TCM is an abbreviation of 'Turner Classic Movies', to which they later oddly felt the need to add 'Movies' in some countries.

I guess it's no different to when people say 'PIN number' (Personal Identification Number Number), which sets off my OCD.

EDIT: Even Logopedia made fun of the name change to include 'Movies' in 2019 on the UK/Ireland channel.

logos.fandom.com