"I do not believe we have ever met, yet I sense my magick upon you. Therefore if I wove the enchantment, I could only have done so at a later point in time." - Venat, Heart of Hydaelyn

"What manner of magick is this, if I may ask?" - Hythlodaeus, Local Busybody

"A traveler's ward, of course. It prevents the corruption of one's aether." - Venat, Inventor of the Blessing of Light, on the Blessing of Light

"Does it protect you from enthrallment by primals, by any chance?" - The WoL, Bearer of the Blessing of Light

"...Primals, you say? I'm not familiar with such beings, but if they "enthrall" by warping the balance of aether, then yes--the magick would afford you a measure of protection." Hydaelyn, Speaker of Plain English

The quest is Travelers at the Crossroads, so you can review the records.

And if you needed the additional help...

"This report seeks to provide an overview of the mechanism by which eikons corrupt and bend men to their will. The phenomenon we call "Corruption" refers to the alteration of the aether of the soul. Said aether normally exists in equilibrium; no one element being more prominent than another. But when a subject is exposed to the aether of an eikon, this changes, their soul taking on the properties of the entity in question." - Owen, Allagan Scientist Specializing in Aetheric Corruption, In a Report Heard by the Scions Themselves

We know exactly what the Blessing of Light is, exactly what the Blessing of Light does, and that it protects from exactly the thing that tempering is, from both an academic source and a personally knowledgeable one. Hell, Venat herself saying this is literally the Word of God about this subject.

Your opinion has absolutely no basis in the text of the story we're talking about. It's just straight-up false, I'm sorry.