Someone can probably explain this better than I, but I believe in Driveline terminology he throws a "rider". He has an over the top arm angle with good extension and good spin.
If he gets the ball up I think it all works and it creates the appearance of a "rising fastball" and will induce a lot of whiffs and pop-ups.
But if he doesn't get the ball up, he's not getting the rising effect that he wants and hitters can punish him for it.
The results haven't been there for Francis yet but I think he will look a lot better against the Rockies in his next start.
If you look at his "Similar Pitchers" on statcast they list Tyler Wells, Tyler Alexander, Bailey Ober, Eury Perez and Emmet Sheehan. That's some pretty solid company to be in when one is hoping for backend starter material.