Judging by the things he did, Muhammad would most likely be considered Not A Real Muslim™ by modern progressives.
The real question is whether Jesus was Christian, given that he was Jewish and predated most of the creeds and rituals that underpin Christianity by centuries.
I like to imagine Jesus, Mohammed, and Buddha all coming back to life and just reading Wikipedia wide-eyed like holy shit guys look at what they’ve been up to while we were away, what the fuck
“And you’re saying this ‘Zen’ stuff is based on my teachings? Also, what’s Japan?”
“So Rome - the people who executed me - made it mandatory to worship me?”
“…My in-laws created a millennia-spanning civilizational faultline over which of them was my favorite.”
Nurse: you’ve been in a coma for 2000 years
Jesus: oh boy, I can’t wait to see how people took my favourite teachings about giving away all their possessions and preparing for the imminent apocalypse!