So, to close the case, the dragonfly Rahi of the BIONICLE Heroes was called an Acid Fly on a random wiki (https://bioniclegames.fandom.com/wiki/Acid_Fly) and I was brave enough to assume it has an official source. After searching for a mention of this rahi for months, I finally find the only one official mention of the Rahi, and it was made by Mutran in BL9: Shadows in the Sky
“Icarax?” said Mutran. “For a handful of Toa and half a village of Matoran? Isn’t that like calling in
a Tahtorak to squash an acidfly?"
So yeah, the Bionicle Games Wiki was wrong, and this sentence is the reason why the Acidfly is a canon Rahi