Yes, suit sleeves are all cut with gussets to minimize pulling the body up as the arms raise.
The period of pleated trousers helps here. The trousers are cut with quite a high rise, it is important not to overfit or scoop out the seat too much. We have to make them look good when they are standing in the fitting room, and also function for what happens on stage. We often start building before they have rehearsed everything.
A colleague of mine put sewn in gussets in the crotch of her trousers. She was worried because she got the guy doing back flips and split russians on stage.
I decided not to, and see if they had any trouble. Theres a guy who does a high kick near the end and he was fine, as was my guy doing splits.
I think it all depends on the period, looser cut legs allow a lot of movement. Tighter trousers need a different cut.