Grizzlies are now 16-2 without Morant. I'm not saying they are worse without him, and they certainly could use his scoring in crunch time in the playoffs, but the fact that they are winning at that rate and over that many games without him doesn't speak all that highly of his value as a player.
So they've beaten Sacramento x2, Toronto, Portland, OKC, Philly (without Embiid), Miami (without Adebayo), New Orleans, LAL & LAC, Indiana x2, Houston x2, Dallas (without Doncic), and most recently, Brooklyn.
It's definitely interesting, but a lot of the time they're beating teams that are either weak or missing their best player. I would probably not read too much into it. Morant's stellar offence definitely outweighs his quite weak defence