Your guess is wrong, unless they bought another chamber, which I am close to 100% sure they did not.
It IS a chamber to simulate high-altitude training, i.e. lower oxygen content, and can benefit any sport with an aerobic component. Rowing and cycling spring foremost to mind. But others like rugby might gain small amounts.
Hyperbaric chambers can be used to speed up recovery from certain injuries, obviously also for diving-related medicine and other specific medical uses. They are hazardous and operated by medical teams, and not generally lobbed into school gymnasia.