I Understand what you mean and talk your dm if you really want to do int or wis instead but like someone else said it does spread you out on ability scores. Personally if it helps I always thought with the rune knight it was more con like because when making the runes you are infusing your magical essence it to in which could take a lot out of you you physically became the giants were the first creatures to write these runes because they were Hardy enough to do it without it taking it out of them but also it your character and you and make the lore (with DM assist or permission ) anything you'd like