Apparently at grassroots I'm hitting 8km on a good day if I check my stats from last season...
I do find the fitness test tougher than the demands of the game, but then I don't think I've ever had a game where I've had to run at decent speed for 12 solid minutes. There's always a lull and a variation of pace in football where recovery can happen - and always one team that will tire earlier causing space to open up and thereby, less movement ends up being required on your part.
About the toughest game I had last season was also 8km, but had a lot of side-to-side running rather than up and down the pitch. Think tiki-taka! That game was really tough and was the closest I've ever come to non-stop running - and that match was honestly a completely mis-match, plus... If I had assistants I don't think I would have run at all(!)