Shorter season tickets still suffer the same "price is based on the concept of travelling 5 days a week" problem as the annual season does for anyone on a hybrid working pattern. Doesn't matter how you try to slice up the year, or how you arrange your time off through the year - if your hybrid contract says you only have to be in the office x days a week (where x < 5), then every single standard season ticket option will see you paying for days you don't use, unless you're one of those people who, as you suggest, could make use of a standard season for non-work journeys as well.
I'm certainly not trying to suggest that flexi seasons are the best choice for all hybrid workers, but they're most assuredly not the joke you seem to think they are - for some hybrid commuters they really ARE the best option, and potentially by some considerable margin.
Biting the hand that feeds IT
