"I thought it was a joke! But ... it's not," Jedrzejczyk told TMZ Sports.
Joanna -- the longtime women's 115-pound champ -- said she would've been fine with her rematch vs. Rose Namajunas getting bumped up to the main event at UFC 223 ... but Max Holloway stepping up is even sweeter.
"He saved the card!" Joanna said.
As for Rose ... JJ's got nothing but respect for the woman who ended her title reign, but says she's in for a rude awakening against Joanna 2.0.
Version 1 was already scary as hell ... so we'd be a little worried if we were Rose.