The doctor is doing something wrong in your example, not the club.It’s not legal if a doctor is falsely diagnosing a lung condition though. Nor is it right in any other way. And I think you know that.
I think it's not that hard to proof Exercise Induced Asthma, as shown by the % of athletes with such a diagnosis in all areas of sports. Only in a scenario like @Bazi described where a club pressures a doctor in handing out fake prescriptions there should be severe sanctions, but I very much doubt that that's the case.
I think I'm just a lot less sensitive to it than most after having followed cycling over the last 20 years. Do everything legally possible to gain an edge. If there's a grey area, explore it and see how far it brings you. All fair game imo. Just make sure you stay away from the wrong side of the line, i.e. blatantly cheating or doing illegal stuff, and I don't have a problem with it.