IIRC this was a mechanic added in Dark Hero Days (which this version is based on), so it wasn't present in the PS2 version. While I can't say if it really works or not (at best there's a quote in-game saying that "some pirates" appear more often in weights), it's worth a shot. You're probably not missing much by going in a specific item instead of a random one anyway.

If you need a more concise source for where to look for each pirate, I'd suggest this one:
https://gamefaqs.gamespot.com/psp/955515-disgaea-2-dark-hero-days/faqs/58415
(search for "EX-08" for the first one in the list)

Nice. Better than just going in blind, which is what I'm doing.

Thanks.

you have better odds of finding certain pirates in certain items there are also minimum floors required for them to spawn but aside from that you can technically find any pirate on any item

Yeah that's essentially what happened. Red pirates too forever to get. Probably around 15 hours of being on level 41 and restarting the game over and over and over and over and over again. Annoying, but I finally got all 16 maps to get to the LoC.