Why not just split the difference and rationalize to yourself that Nezram is the one regaling his tales while at the Yawning Portal?
Nezram: "All you adventurers have it easy these days! You think that Undermountain is the ultimate dungeon?! You just kick back have a few brews and hop down a hole in the floor! Back in my day I had Walk between Worlds, Uphill, Both Ways to find a decent Dungeon! There was this one dungeon on a world called Oerth..."
Adventurer: "Earth? I've never heard of it..."
Nezram: "I said Oerth not Earth! Don't distract me or I'll start ranting about the Imaskari abducting Egyptians and Babylonians through Portals..."
Adventurer: "What the heck is a Baby Loon?"
Nezram: "Oh, to the Nine-Hells with it! I'm tired of this nonsense, I'm going up to room to go to sleep..."
Adventurer: "Phew, any more wizard ramblings and I was going to fall asleep in my Mead-Mug... Maybe that's why they call this place the Yawning Portal..."
The very next morning...
Nezram: "Oh, good you adventurers are still here! When I got up to my room I was so aggravated I decided I'd rather sleep when I'm dead, and seriously considered turning you into a toad. But, you're in luck, I'm a very forgiving wizard, and since your ears don't work so well, I wrote the dungeons all down in a book for you entitled
Nezram's Tales of Adventure."
Adventurer: "Huh? Who the heck is Nezram?!"
Nezram: "I AM!!! Oh, why did I ever come back to Toril? Nevermind, I'll call the book
Tales from the Yawning Portal."
Adventurer: "Wow! That's a great title. I think I've heard of a tavern called the Yawning Portal. Weird..."
Nezram: *sigh* "Why do I even try? You're sitting in the Yawning Portal right now!! Just read the book so you can know what a REAL adventure is..."
Adventurer: "Ummm, my dad always told me the Sword is mightier than the Pen, so... I don't know how to read. Maybe you could just tell me the story over a few brews?"
Nezram: *shakes his head* "The adage is that the Pen is mightier than the Sword!!! ARGH!!! Maybe the people of Earth will appreciate this book." *ZAP*
Adventurer: "RIBBIT...RIBBIT..."