According to that study done using normal dose 200 compared to 800 wich is half the daily dosage allowed out of 1600microgram Salbutamol (max / 24 hour)(Wada) you gained 13.8% muscle performance over placebo during 100% sustained action 72 contractions before fail vs 82 contractions before fail on 800mikrograms, now let's say 63% or whatever in a starting 11 of the players get that gain due to having 'asthma' and given the start stop nature of football the gains during real life situations could be even larger when you factor in interval rest. That's one hell of a collective boost to performance if it holds true.
Those poor 'asthma' sufferers of course can get another legal dose of 800 more at halftime too if they have symptoms of 'asthma' or report being winded and still be within regulation
. Most studies are unfortunately pretty old by today's standards and they compare normal doses of 200microgram, not 800 twice, and even fewer focus on systemic adrenaline effects on large muscle groups. The data are inconclusive and thats why the practice is allowed probably.
Well worth noting is that Asthma is around 8% in a normal population and those countries with lots of asthma are at 11% population wise. Some clubs in that article must be very unlucky to have as much as 63% of their players suffering.