It's the same square dance, how come the difference is so big

Yes, indeed.

There is a direct relationship between the composition of each square dance team, the age difference, the amount of dance training, the inspiration of the dancers, the dancer's 'Fan' or lack of it, and so on.

Sometimes the 'tacit understanding' of practicing together is also very, very important. Even the unity within the team is directly related to the overall temperament.