Or that one is the mess-up and all the quests that imply the PC is the only one by dint of having to be involved if anything needs doing in the Maw are better evidence.
There isn't an absence of evidence here. There's evidence of absence, specificially that there's nobody else who can sensibly operate in the Maw.
Ugh, that had me rolling my eyes all the way from Darkhaven back to Sinfall. Yeah, sure, you're oh so selfless and redeemed. Shut up and throw more fireballs.