Toilet drains into two different containers for each type of waste. The urine holding tank periodically vents overboard. The feces canisters are stored and returned to earth.
The ongoing problem is that the urine holding tank is not venting into space very well when they open the valve. The toilet drains both waste types into their containers ok. But since the urine holding tank is about the size of an office trash can, it can fill up very fast.
I believe two of these are naval aviators, and they would take exception with the “army” characterization.
But you’re generally correct. It’s very common that astronauts will not only have a military background, they frequently are active duty military officers on a long term detail to NASA.
The army is not well represented in the astronaut corps, because the US army only flies helicopters under an inter-branch coordination agreement.