I agree big time! Its been getting on my nerves for years how British producers get away with calling a sequence of 5-6 episodes "a season".
In America you have "Seasons" over here we call it a "Series", and your average series has always been shorter than your average season (with a couple of exceptions)
American seasons are generally longer and always have been longer than the average British series - it's nothing new and has been going on since the 50's. Remember in America you have whole scriptwriting teams and unions, whereas over here most good dramas and comedies are written by one or two people.
British producers aren't "getting away" with anything.