I'd heard that somewhere before (though I can't remember where) and I'd like to know if it's true. If it is, I won't need a PS1 emulator as I already own Null DC. (I couldn't get a physical Dreamcast unfortunately)

Is is true?

No

I guess Bleemcast! was supposed to be commercial emulator that allowed playing PS1-games but otherwise, no.

Yes, Bleemcast is what pretty much cemented emulators as a legal thing, although the creators had to close down despite winning the lawsuit because of their legal fees. That said, it's probably easier to just download ePSXe if you want a Playstation emulator because Dreamcast emulation is somewhat problematic.

That clears that up. Thanks.