I post them on both when I make a new action (ecosys + forum)..but thats mostly because Ecosystem was still growing. Now that its basically the staple, go-to way to get new actions and has a pretty large userbase maybe that isnt needed.
At this point it's probably fine to post them to Ecosystem only, but since you still need a way to notify everyone of new stuff there should still be a forum post for news.
Maybe the next iteration is for Ecosystem to become self aware and have a feed of the latest changes