Combat SAMBO definitely isn't BJJ but at the same time it's similar in that there's a LOT of submission grappling. Fedor reached the absolute highest level in SAMBO, like Roger Gracie in BJJ.
Combat sambo is NOT the highest level of submission grappling and it does not put him on level of a roger Gracie. Aleks reached the highest level too.....
Depends how much stock you put into SAMBO's submission grappling credentials I guess... But I would think without question that prime Fedor's submission grappling is many, many, many leagues above Cormier's... The fact he stopped grappling almost entirely despite it being what made him great, probably says something about his body's ability to physically handle grappling.
Again, you can’t elevate combat sambo to that level. Fedor is definitely better at submissions than dc and more likely to catch dc than vice versa, of course. That doesn’t mean he’s going to dominate all grappling exchanges or that it’s likely he’d get a sub.