Well, the code in KC3Kai is also not set yet and could be changed if others decided to use something else, and enkcwiki have not given any abbreviation for the ship class yet. And as I said above, poiviewer is currently using DDE, which is neither DE nor PF. As such, the code DE have still yet to reach the status that "everyone's using them" so there are still space to operate.
However, outside those tools, most of the discussions I have seen surrounding kaibokans seems to be adopting the code DE pretty quickly, which is also something to be considered.
p.s. another argument for DE I have seen elsewhere is that devs call them escort and thus it might be better to base on what devs are naming them instead of reclassifying them into frigate.