^^
One general problem with that is requiring an additional match day at the end of the season. A bit of logistics work for Nordeus, but you may also have noticed managers complaining already of having too many matches to deal with...
An issue specific to our game - The league winner should be the team that did the best over the whole season; but in T11, teams change in quality and composition over the course of a season and end of season might not reflect the rest. Should a team that slumped the first 12 matches then bought in half a team be rewarded at the end of the season? Same reason players on the "best rated" chart have to play a set # of matches.