Not saying he couldnt bc the UFC HW division is atrocious and thin full of fat lazy untrained bums, but he fought a 0-0 guy and a dude who was 2-1. You can pick a random Joe from the street and he'd prob be a UFC top 5 HW.
Greg Hardy was also 3-0 with finishes in like 10 sec in his first fights, then went to the UFC racked up some wins since the division is terrible, but got destroyed by even average fighters.
Even Bo Nickal who has the striking abilities of CM Punk looked like prime Canelo vs all the bums he fought at the beginning of his career and these guys are p4p goat level next to the dudes Stevenson fought.
Lets wait till he has 3-4 UFC ranked fights...