I am pretty sure that was because Voldemort couldn't get the sword. Like, he was unable to access it.

Isn't Harry technically the Gryffindor horcrux? Maybe Voldemort didn't want a Gryffindor horcrux because Slytherin and Gryffindor were rivals. I do remember that before the 7th book came out that it was theorized that the Sorting Hat was a horcrux since it belonged to Gryffindor.

I mean I don't think you can make something goblin-made a horcrux?

Sorry if I'm being stupid

It's because voldemort didn't want a gryffindor horcrux.

I thought that was explained in the books

Like how hogwarts was so special to voldemort that he used things belonging to hogwarts

But then he would clearly hate to have his soul in something that kinda is gryffindor