No idea. I just know you can't use the custom variations and each character has two defaults.
It's stupidly more complicated than that for no real reason.
1: Each character has 2 default variations equipped. These are NOT the tournament variations (or at least a vast majority of them aren't)
2: Each character has 6 or so presets that you can choose from if you dont want to mix and match yourself. These are found by pressing 1 while in the Abilities section of customizing a variation.
3: Only 2 of the 6 presets found in the above list are for tournament mode. They are marked by a little trophy symbol on the left.
4: To practice or play with these tournament variations outside of ranked, you'll need to either change the defaults to the tournament presets or make new variation slots and set them to the tournament presets.
It feels like a MASSIVE oversight that the tournament / ranked variations aren't the default 2 equipped ones for every single character. It's not a HUGE deal and is quick to fix, but that doesnt change how absolutely mind boggling it is that they didnt think to line up defaults with the predetermined rank play variants.