I also posit they are using housing exactly as SE intended. SE considers alts as unique characters not alternate identities of the same player. Following this line of reasoning it makes sense that SE intended for alts to have their own houses.
And yet, Square-Enix had to go out of their way to implement rules preventing alts from buying houses in 4.2 onward. You can't honestly tell me that Square-Enix 'expected' people to buy houses for their alts when there wasn't enough houses for everyone. I imagine Square-Enix never anticipated people to buy houses for their alts, and by people taking advantage of a loop-hole that resulted in hurting the experience for other players did it cause Square-Enix to step in and prohibit toxic behavior.