In an interview with a brony podcaster named TookKriticY2k, M.A. Larson was asked about his future of writing for pony. Apparently this happened last month, but flew under the radar.
In the response, he had quite a bit to say about how the show used to work back during the Lauren Faust era vs. today, along with the challenges of working from Los Angeles on a show being produced in Canada. It sounds like pony has a lot of hands in the cookie jar now that it's so big. We even got an extra dramatic ending to "Make New Friends but Keep Discord" with a much darker Discord.
The details can be found in the podcast itself. Head on down below to listen to the explanation straight from the source!
Skip right to the question at 42:30 here.
tl;dr - Larson needs full control over more episodes, cause Amending Fences was amazing.