How to balance a more intelligent Phantom?

I have some concepts for NPC/PCs with intelligent (Int 10) Phantoms.

For some reason Paizo thinks companions with Int above 7 are too powerful to start with. I have no idea why.

So how would I balance it out? I'd rather not mess with the other Ability stats if possible.

Any ideas?

I just gave them 10 Int from the start, hasn't caused any issues yet.