If you take a look at the Ofcom document linked above, the reason a "subtitle' caption is on the idents is explained at the top of page 22.
A1.21 Publicity: the word ‘Subtitles’ should be displayed legibly on the screen at the start
of the programme.
So technically Channel 4 and others who don't show a Subtitles DOG
are in breach of the Ofcom code. Interesting!
Which includes CBeebies...
Anyways, CBBC started to use Reith on their promos. In the future, the Subtitles DOG might be Reithed... We dont know
BBC News. The home of cock-ups.