We do however have a sketch from Hussie that showed Terezi in his regular style that had the long elfish ears!

I assume you’re refering to this sketch

but this sketch came out around the time of the trolls introduction and I can’t find another instance of Hussie-drawn trolls with ears so it may have just been a preliminary sketch or an aspect he dropped.  Hussie also has a tendency to draws ears kinda big shown in some of the Hussnasty style panels  so it might just be because of that.

Not directly related to this ask but as a disclaimer: I’m not saying you’re wrong if you choose to hc trolls with long elf-like or fox-like ears, but there is no certain canon about troll ears so please don’t use the lack of canon or the small amount of it to try and force people into headcanons.