The part I don't understand is why they sell you a 50 caliber to shoot a 45 caliber. Why not just buy a 45? Do sabots make the 45 fly better? Is it to too hard to ram a 45 caliber down a 45 caliber hole with metal to metal contact?
Unless you hunt in the Northwest where the bullet must be the same size as the bore (or words to that effect) - the sabot gives you a lot of forgiveness in various “.50” caliber bores.
Some manufacturers are toleranced very tight on their bores - others, not so much. The sabot levels some of the variation, gives you an easy load effort, and good gas seal.
Using good quality lower speed expanding bullets (handgun) gives you a huge selection of options for ranges and game. A fast moving handgun bullet with speed and impact energy at 100 yards isn’t a bad option to have.
There’s nothing wrong with a bore riding heavy lead bullet - plenty of game is killed by them each year. But - it can be a bit of witch hunt if you have to the perfect seal without knowing your exact bore size out to 3 digits.
As far as .45 or .50 with sabots - some states regulate the minimum caliber for game species. Some don’t allow sabots - so there’s a market for bore riders.
I equip a program with muzzleloaders for an Eastern whitetail hunt each year - we run .50 because 99% of the time - I can count on the needed supplies being in stock. We’d be fine with .45 caliber rifles, but the .50 caliber with a sabot lends itself well to .45 caliber bullets in a sabot for all around use.
