The "you can only wear a leo to get used to only wearing a leo" is the silliest thing ever. It makes absolutely no sense. None.
Really a mock meet/dress rehearsal is more then sufficient. Both gyms we have been at do this. One "meet/practice" prior to start of meet season. So we all (parents, coaches and kids) are OK with things like is the hair in the way, is it going to hold up, leo fit and in good condition, no undies showing and so on). This makes sense.
Leo's only for getting used to them. Makes no sense. Getting used to the leo is the least of things regarding meets. They have to get used to being judged, the added crowd of spectators and noise, different equipment (that changes at every meet). The view from the equipment (which changes are every meet). Hair if they are not used to whatever "meet hair" is even more important then a leo.
Grips and supports more important to get used to.
Kids competing multiple times a season for years, do not "need" to get used to a leo. And if they do then they need to get used to the actual leo they are wearing, not just any leo.
And I do not see that happen in any other sport or activity that requires a specific dress or uniform. At least none I or my kids have ever been in.
Just silly.