In Kung Fu, low stances are important for making your movement agile and creating your foundation for footwork. Leg strength is always an important part of stance training also but the height is less important than people think.
In fighting terms your stances are higher by default if your fighting stand up, lower stances are only really engaged if your slipping, evading, striking low, changing angles or engaging in a take down (Chin Na) or floor fighting. Stances should be strong but above all, agile and adaptably functional.
One person's higher stance with strong legs, correct weight distribution and the ability to flow in and out, is far more important than someone just squatting their horse stance as low as possible because they were taught height mattered most.
At the end of the day, martial arts is not a limbo contest.
A number of students who are less flexible can have very strong legs and have excellent Kung Fu skills. Although training for full range of motion is ideal, it doesn't mean that your Kung Fu is lacking because your stance isn't level.
Should you push for low stances and stronger legs, YES. Should you relate someone's low stance to having good Kung Fu and an ability to actually use their techniques for real, NO... It could just mean they are more flexible than you.
Interested in joining Spectrum Classical Kung Fu? We have a new pay-as-you-go Beginners session every Friday night, with more advanced classes available during the week, in addition to bespoke, private tuition. Please feel free to contact me directly for information.