I've been alerted to a few tiny forms, like glowing Aeons and "scaleless" Luminas, occurring in the Encyclopedia recently. If these forms made it, there is no reason why the permanent plain-winged alt of the Solstice dragon is not also included. Bred-only forms occur for other dragons and show in the Encyclopedia, as do the alternate Aegis (from their BSA). Curled black hatchlings show up for goodness sake.
So yeah, in other words, I would be interested in seeing the alternate Solsti
3 Terrae entries is a bug that will be fixed. (though I should note that, since the sprites are literally the same, you don't have to hunt down and click adult "alt" terraes for a specific row to unlock, only eggs. I just checked my own data and I apparently have not clicked many adults of one variant, but have all sprites adult).
Only having one solstice entry was something I recall being an intentional decision, but I don't recall the reasons, which means they might not be valid an