Mathilde is very devout person with lot closer familiarity to the divine than most people have, probably including Teclis.
Also, no matter how smart, experienced, or eductated you are, you can still make mistakes, often especially if you are well educated and experienced and bump into something that goes against your education and experience.
So either Teclis was right, and divine magic is just like wind magic except priests are just silly for not realizing it, Teclis was lying and intentionally misled his human students for some reason, or Teclis was wrong.
Of the three, i find Teclis intentionally misleading his students in this case to be least likely.
I am also very suspicious of him just being correct, there seems to be more to divine casting and the gods than just mechanistic wind.
So that kind leaves me with just Teclis being wrong, and elven arrogance arrogance and not taking time (because he was kinda busy with this war thing that was going on, and then had to go to Ulthuan and never got around to visiting again) to research properly while refusing to admit to not knowing shit in front of all these humans seem like the most likely cause.