Did Matoya just possess Y'shtola's body?

[Cilia]

I don't think there's any lore supporting this at all, which actually does make me a little annoyed, because I'm seeing this claim everywhere (Reddit, Tumblr, Discord), taken as gospel truth.

It's as bad as "FFXIV is the same world as FFXII".

I've mentioned it before, but I don't use social media. I'm not saying it's truth, it's just what makes the most sense to me with the least amount of shenanigans. While possession isn't outside the realm of possibility (even without the Echo), it seems far less likely than the simpler "Master Matoya is just a title."

Again, not arguing it's a hard truth.

Matoya is a recurring name just like Cid, Biggs and Wedge so I really don't know why that theory got so much traction. Let's say Matoya is the old witch's title. What is her real name? Why Y'shtola (or even the porogos/broomsticks servants) never allude to the fact it's a title? Why they don't hint to her real name? Why introduce that new fact in the MSQ after 2 expansions? I'm positive Matoya is the character's name and not a title.

Before XIV, Matoya was only an actual character in I. There are vague allusions to her elsewhere, but that's not the same as being a character. (Cf. Doga and Unei, who have allusions to them elsewhere but are only actual characters in III and XIV.)

Everyone might just refer to her as Matoya because they don't know her real name.

If we're going to go crazy with the possession theories, though... who's to say Urianger isn't being possessed (by, say, Unukalhai) as well?

When we go with the possession bits thing spiral into insanity... which is why I don't want to use it.