You can’t flip flop and shoot when 10 round minor is at an advantage to a stage and then go back to major. But if you’re shooting major and don’t pass chrono, there is no disadvantage to going to a 10 rd minor back up gun.
Flip it the other way, if you shoot 10 rd minor in single stack and that gun broke and you had to had to go to back up gun which was 8 rd major, you’d still be shooting minor. The gun is still legal for division.