Well I don’t particularly remember the Spivac fight, but I SURELY wouldn’t consider him a litmus test to see who’s a good grappler in the division. Not being taken down by him doesn’t mean you can grapple, he’s never even approached the title picture.
As far as the Ngannou fight is concerned, I remember watching it and being stunned how badly he was losing to Francis on the ground. The guy had absolutely nothing and only lost because Francis could hold him down. Myself and the people I watched with came away from that fight saying he had zero grappling. That fight is the entire reason I knew he’d lose to jones very easily