Twizzels on one leg

Actually all top dance pairs change feet between first and second twizzel. I believe that it is more difficult to stay on one foot all along and it brings higher level (or should). And weaker dance pairs do that sometimes. How is that?

There are many ways to get features for the twizzles. Most top teams simply choose to do an additional set of twizzles instead of doing the first two sets all on one foot, especially since they are graded on how fast they are in the rotation and how much ice coverage their twizzles get. Doing two sets of twizzles on one foot would make it harder for the second set to achieve that.