The industry norm is actually to have teams working on multiple projects at once, and broadly speaking it's a good thing because it helps prevent lay-offs by staggering the stages of development across multiple projects, so that devs that wouldn't have much work to do during a certain part of the development cycle can work on something on the other project during that cycle. I'm personally unfamiliar with whether the development of MMO's would introduce a meaningful difference that would make this model less necessary, but regardless I don't think this is anything to get upset about.

In addition, it's not like CBU3 is splitting their bandwidth here; every individual project requires distinct funding, so for CBU3 to be working on multiple projects at once, that strongly suggests that Square-Enix didn't fund FF14 enough to fully employ everyone already working at CBU3. And again, that's not necessarily bad, because it's normal for teams to work on multiple staggered projects at once to prevent lay-offs so that folks in all departments always have something meaningful to contribute to. Which is to say, if they didn't have this second project to work on, it's quite likely that the team would be reorganized in a way that reduced their headcount, which would probably be bad for everyone, including the players.

In short, I would recommend not reading too much into this.