The game was never released by Bandai or Sony for the PSP. Any mention of an “exclusive” usually refers to one of two things:
To ensure your Digimon World 2 EBOOT runs without the common crashes or glitches associated with PS1 emulation, follow these steps: The POPSloader Requirement eboot psp digimon world 2 2 exclusive
When you see , it refers to a fan-converted or officially dumped version of Digimon World 2 packaged as an EBOOT.PBP. This allows the game to run natively on a PS Vita, PlayStation 3, or (most importantly) a hacked PSP via custom firmware (CFW) like PRO-C or LME. The game was never released by Bandai or Sony for the PSP