Yep same here, I was not fun of Sylvaneth Arch-Revenant model till I built it myself then I just saw how amazing it is. Those Kurnothi look better from some other angles.
I took facebook groups popularity which can be some factor. Also you got good points there about small suppprt other aelves are getting but I expect that will change soon.
Wanderers are most popular aealves without battletome, they really could get update and tome even without making new range of models, maybe new hero in that dual box everyone is mentioning.
Sylvaneth warband for shadespire got warcsroll and there are some new keywords so their tome is around prob. Also I never saw shadespire band with weapons they are not using in AoS so we might se maybe new kit with revenants with bows.