I’m not disagreeing about him being the ancient tree stump. But Zelda says the tree was inhabited by a “dignitary spirit”
Honestly, I don’t understand what is so different from my thought of Calamo becoming a Deku Tree, & the SkSw Tree becoming a Deku tree.
Nothing confirmed, just reading between the lines.
However, Calamo's tree is hard confirmed as The Ancient Tree Stump from BotW and TotK.
It doesn't have a face at the end of Age of Imprisonment, and TotK's voice memory mentions an ancient spear that was found within it.