It seems like you’re taking your own assumptions and trying to make them general. None of that is true in, say, Eberron. (Well except the part about magic being tech) Nor is it necessarily true in FR.
A lot of spell dev will be wizards, sure. But I rather doubt Ensaring Strike was thought up by a Wizard.
And Eldritch Knights are...smart.

Like their secondary stat is Int. I’ve never seen one played as anything less than very smart, and I’ve never seen one played as though they were a fighter who a Wizard came and taught some spells to.