As much as I would love them to be exposed cheating, comparing average UK population to a squad of professional athletes who are extremely valuable assets where their bodies are under constant medical scrutiny is a bit disingenuous.
I swam at a reasonably high level and asthma was fairly common amongst international level swimmers. When you are training at a certain level (which whilst amateur athletes think their routines qualify, they do not get close) you notice little things because of the fine margins you exist in. I brought up breathing concerns once when I was in my teens and was given an inhaler for "sports induced asthma". Had the inhaler until my swimming career ended in my early 20s. I wasn't the only one and it wasn't something that was nefariously handed out - I wasn't a high enough level swimmer for that to be a thing, but I did train with some seriously elite swimmers at one point and inhalers for sports induced asthma were common.
I swam at a reasonably high level and asthma was fairly common amongst international level swimmers. When you are training at a certain level (which whilst amateur athletes think their routines qualify, they do not get close) you notice little things because of the fine margins you exist in. I brought up breathing concerns once when I was in my teens and was given an inhaler for "sports induced asthma". Had the inhaler until my swimming career ended in my early 20s. I wasn't the only one and it wasn't something that was nefariously handed out - I wasn't a high enough level swimmer for that to be a thing, but I did train with some seriously elite swimmers at one point and inhalers for sports induced asthma were common.