User blog comment:Xilinoc/Grammar, wording, cleanup, and out-of-universe wording/@comment-5675229-20130321002426/@comment-4957813-20130321002754

We only use past tense in history sections, or if a character states that so and so used to be something. It's for preventing people from spoiling themselves too much, if they are in the middle of the arrancar arc and see Ulquiorra was an Espada, then they'd realize that something must have happened to him, cluing them in on the possibility that he is dead.