Firstly, I didn't accuse Yoshi-P for lying, do not put words in my mouth. My own words was:
I also went further to mentioned that even if his explanation was valid, it (glamour log) can still be done somehow as proven by other games and it's in high demand from the players.
Now, with that out of the way, let's get back to the data type. Note, as I do not code the system myself, this is all purely speculations on my side based on the BRIEF knowledge I have on coding and observations from playing the game as well as some logical prediction. In no way am I claiming this is exactly how the system works, just a disclaimer before someone put words into my mouth again.
I definitely disagree that an entity in the inventory will carry the same amount of data than an entity found in the proposed glamour log. Two reasons; size of data and read/write frequency.
An entity in the glamour log should rightfully hold similar amount of data as one found in the armoire, striped down of any excess information such as color state, spiritbond amount, item condition, etc. It's basically strip the item down to the bare minimum amount of data. Meanwhile, an entity in the inventory has to cover everything that can be found in there. Be it consumable item, gear, tokens, collectible, etc. Logically deducing, (Is this a grammar mistake? Meh) a data entity found in inventory should be proportionally larger than one found in armoire, and by extension an entity in the proposed glamour log. That's one.
Next up, read/write access. We all know that FFXIV has a backup ongoing in the background every couple seconds (I forgot the exact number, someone please enlighten me), in case of data corruption and a rollback is required. I believe this is the exact reason Yoshi-P once cited to be one of the obstacle in simply increasing inventory space. Once again, I believe everything carried on the player aka anything inside inventory and armory chest, is subjected to the X seconds refresh mentioned earlier. On the other hand, an entity found in the glamour log should rightfully behave like a data entity found in the armoire and retainer's bank, they will be access only at specific locations and time, without the on-demand capability unlike inventory/armory chest.
So if logically speaking, a glamour log required lesser data and are access less frequently, I believe I'm not entirely wrong to say that Yoshi-P made a bad reply (put in bold so you can stop accusing me) if there's nothing lost in the translation to and from him in that interview.
As Captain Jack Sparrow would had say (I'm been watching Pirates):
Savvy mate?