It seems SE sees apartments as Housing

[Avoidy]

It's funny because the picture OP posted is written to imply that players who buy this game can easily obtain both forms of housing. Phrasing like "Let's build a house alone or together with friends! You can also decorate your own room." implies that on top of building a home, you can also have an apartment.
For this to be an honest ad that tempers people's expectations to reality, the actual picture of an outdoor housing plot should be nuked and replaced with a picture of the apartment interior. Use of the word "mansion" should be removed as well, because let's be real nobody's getting one of those.

This is the rare moment where the English translation being vague and radically different from every other version actually works in its favor a little bit. You can't define a "little slice of Eorzea," so fans have less room to be upset when the house they expected to own never comes to fruition. Players in other languages however, have absolutely been misled by this ad in particular, assuming the translations I'm reading in your pic are accurate.

[Toutatis]

. Use of the word "mansion" should be removed as well, because let's be real nobody's getting one of those.

The French version doesn’t say mansion, it says “house”. “Maison” is “house”, not “mansion” though the term is generic enough to include a mansion or a small house but not an apartment. Whoever translated the advertisement from French made a mistake.

This is the rare moment where the English translation being vague and radically different from every other version actually works in its favor a little bit. You can't define a "little slice of Eorzea," so fans have less room to be upset when the house they expected to own never comes to fruition.

They still just show a house on the picture and to me the expression is directly derived from “a slice of land” which refers to a of a piece of land in Eorzea. It’s not an expression one would use to refer to an apartment.

[Avoidy]

The French version doesn’t say mansion, it says “house”. “Maison” is “house”, not “mansion” though the term is generic enough to include a mansion or a small house but not an apartment. Whoever translated the advertisement from French made a mistake.

They still just show a house on the picture and to me the expression is directly derived from “a slice of land” which refers to a of a piece of land in Eorzea. It’s not an expression one would use to refer to an apartment.

Yeah I 100% agree. Not sure if I wasn't clear 'cause I wrote that when I got up, but I look at that pic and feel like it goes against OP's thesis that Square see apartments and houses as the same thing. They clearly see them as separate entities, which is why they tell players that they can own both, not just one or the other.