Yeah, I have just talked to some historians over this.
But basically, here's their following arguments why DE should be chosen:
- Classifying them as PF because they're called Kaiboukan is silly, since they were used as escort ships as well. The intended role of the IJN ships doesn't mean much when classifying them, since the IJN used battleships as tankers, submarines as troop transports and destroyers as supply ships.
- One of the argument is that DE carried torpedoes, while the Kaiboukan doesn't. By that logic, the Evart-class DE should be a PF, even though the USN has classified them as a DE. In fact, the Shimushu actually have a better range than the Evart-class ships.
- Another argument is mainly that the industry of US is way better than the Japanese, which allows the US to outfit their DEs with torpedoes.
- The River-class frigates, which are basically USN PFs, were also classified as DEs, due to them not being used for coastal duties.
Seems like I can't do much, until these points are cleared up.
UPDATE: I have received undeniable proof that they are referred to as PF according to the following 1945 USN Reference Manual. This seems to be case closed now, I will revert everything back to PF and push the conclusion to the other places.