All their more general points in the post are perfectly valid arguments for focusing on a single database that I've heard from other projects, but naming specif

All their more general points in the post are perfectly valid arguments for focusing on a single database that I've heard from other projects, but naming specific technical issues like that actually makes it seam more nit-picky and less valid. I'm not sure many people would have found anything to argue with them about if they had simply said "Tagetting multiple DBs requires more resources to develop and test, limits our ability to make the most of what Postgres offers, and increases the cost of support. The proportion of users using MySQL is decreasing, so we have decided to focus on Postgres to give the maximum benefit to the largest group. We understand this may cause issues for some users so here is a comprehensive migration guide/toolset".