I'd guess very few.
They probably had a way to test it on non-Andalites (if a buffalo can do it, why can't a kafit bird?).
Moreover, the time-limit probably is a fault built into whatever physics the morphing tech uses, which would allow whatever scientist that understand those rules to deduce that there's a time limit before the transformation becomes permanent.
Which is what happens in good experimentation. Andalites seem like good scientist, but maybe they got lazy
