Some armed professionals & concealed license holders like the comfort or smooth draw with a FBI/canted holster. Newer polymer & Kydex holsters like the Blackhawk SERPA & Blade-tech line allow minor changes to the same holster for drawing or comfort.
I used the FBI cant with my M&P full size 9x19mm in a SERPA and honestly didn't like it as much as the standard or vertical carry. I have large hips & the M&P pistol looked a bit like John Wayne in some of his later westerns,
It may work better for concealed holsters or when worn; behind the hip.
I sometimes wear cross-draw style rigs and they work well with angled draws.
I wouldn't suggest that method for regular duty or open-carry positions.
PS: If you ever see the old crime drama; Sharkey's Machine(1981) with Burt Reynolds, he wears a wierd leather FBI cant holster but in a crossdraw for his full size 1911a1 model .45acp. In real life, it'd be a awkward draw to use for a large pistol.