This is true for schools (heck, I only had 4 max ever) but for a large gym, it's probably not as hard as you think, either.
You may not be able to do it in person, no.
But if you have more than one or 2 Worlds teams and a 2 week filming window, it's not farfetched at all.
Example:
(Disclaimer: I am not accusing anyone I just need a Mega Gym for an example.)
CA Plano has Wild, Panthers, Crew, Ladycats, Swoosh, Cheetahs. See also: super talented J6. If I need a brunette base (who is ever looking specifically at bases?) of average height to illegally fill in on Panthers and film at some point, the possibilities are endless. Particularly if that's all the person does in the routine.
See also: Backspots.
Rarely does one even see a backspot's face. Lady Gaga herself could be backing that stunt and you would have no idea.
See also: coaches. No one knows what every single coach at a program looks like. Suzy who just aged off the Worlds team and coaches Minis could totally fill in on her old team.