My interpretation is that if they were going to increase character data, they would just give us more general inventory space rather than doing something like a glamor catalog (or fishing tackle box).
They also explain that FF XIV character data is already much larger than other mmos, so direct comparisons cannot be made.
If they add lots of features that increase character data a lot, then they will no longer be able to make backups of our data as frequently as they do to protect us from rollbacks if we DC or the servers crash.