For an example, the skaven battalion "Congregation of Filth" has a unit entry of a "Plague priest on plague furnace". Here the sub-heading is "on plague furnace". And it can't be ignored
This is the same for skyborne slayers, it states Lord celestant. That is the full name. There is no sub-heading cause the full name is described. Heck it even came with a battlebox. It states : Unless it included in the entry for the unit. On both casus the full name is described.
I feel like we be rule bending to our advantage here. And going with a lord celestant on stardrake cause the unit entry is lord celestant and we want it to be any lord celestant is kind of lame. With battalions in our battletome these discussions are fixed but now we be talking about a very old battalion and we know the intention of that battalion. That intention didnt change with the new wording.