No, 90 songs was never mentioned anywhere. That is just simply the number given by Takahashi when he said how many songs Sawano composed for the game. That had nothing to do with the CD release.
That's what I mean. If this game has 90+ songs according to Takahashi, why the soundtrack is only 55? I hate when they do stuff like this in soundtracks. Doesn't make any sense to me.
They never confirmed the OST will be 5 CD in the first place. Kinda sad though that the official OST will only have slight more than 1/2 of the total songs.
I'm pretty sure I read somewhere about it being 5 CDs... I'll post if I find it.
EDIT: They changed the info after the update. It says only 4CD now. Weird because CD 4 is only 8 tracks... And some songs have several versions like "in the forest". Kinda disappointed we won't get the whole soundtrack this time...