Probably not due to flash directly, but flash is a pain in the ass to work in, so I could see why there would be lack of enthusiasm to dive back into the code and implement things lol
Because it's a mobile game and mobile games need updates to prosper. In all fairness they left SWL to die until the Endless Deads update game out (many months later) since they were hardcoring ML. But a mobile game can straight up just not be left without updates, which is why they returned.
While desktop games i.e. SE don't?
Following the logic wouldn't they then update SE because that is dieing like Legacy was. I believe they update Legacy because for some reason they would rather work on that game than SE. Either it's more fun, lucrative or better long term as it's on mobile due to larger player base.
At the end of the day all I would like from the developers is for the stick series to 'live' in some format. Which ever way the devs prefer. Like you I would like clarity over SE but I don't think (unless your know) we are going to get that.