Assuming Ruby will still get title credit when she’s not the main companion. But I’m sure they’ll find a way, remember how fast they went through names in Journey’s End.
Did Freema Agyeman get a title credit when she came back for a few episodes is Series 4? I do not remember, but that’s probably the closest comparison for Ruby this reason.
Yes, she did
Then I assume Ruby will probably get a title credit in the episode(s?) she’s prominently in, but we will see.
Did Bonnie Langford get title credit for any of the RTD2 ones she was in?
I don’t think so, but she was never really in the companion role other than arguably Empire of Death, but even then she spends like half the runtime as Sutekhs minion.
Wondering on it is less about the time and more that it’s a much more involved change to make with these titles, with the names being interacted with by the TARDIS and all that.
I’m sure they’ll do their computer stuff and make it work fine.