Different rules exist for different variants of HFT; they don't all follow the UKAHFT model specification.
SWEFTA allows sitting on a bag, but it also allows targets out to 55 yards, both obvious similarities with FT but nevertheless HFT in SWEFTA is a very different game from FT, and we have some who shoot just one and many that shoot both.
SWEFTA also adopts a modified Sporting rule that allows you to focus the scope for every target, however this has to be done before you bring the scope to your eye. If you forgot, too late.
It's all part of being inclusive; many of the SWEFTA shooters left their teenage years behind quite a while ago, and getting down prone - let alone getting up again - brings its own difficulties.