Remember, the YouTube sensation went the distance with Mayweather in June -- even landing a few punches on the undefeated champ.

There wasn't a knockout during the bout ... which pissed off every boxing fan and gave the Paul bros. the bragging rights to say Logan went 8 full rounds with one of the GOATs in boxing.

But, Floyd says no one should've been surprised there was no KO ... 'cause it wasn't a real fight.

"People have gotta know, there's a difference between a real fight and an exhibition," Mayweather said this week at the WBC convention.

"I did an exhibition with the YouTuber Logan Paul. We had fun."

Now, for a REAL fight, Mayweather pulls out all the stops when training for his opponents ... even chopping wood like he did before his Manny Pacquiao fight in 2015.

But, for Logan, Floyd says he wasn't even training that hard.

"All I did was work out from time to time," Mayweather said, "If it was a real fight, it would've been a blowout in the first round."

Funny thing is, Logan told us back in July if he got a rematch with Floyd, "I promise I'll knock him out. Promise."

Well, money talks -- Mayweather reportedly made at least $30 million for the Logan fight ... and like he says, "When it comes to legalized bank robbing, I’m the best.”