This is more of an argument against the terminology "borrow" rather than the action. Naruto doesn't have to borrow chakra from Kurama because Kurama willingly gives it to him. This wasn't always the case, but Naruto's bond between him and Kurama put's him in the position where he doesn't need to ask for power. So, no, Naruto is not technically "borrowing" power, but Kurama is giving him power, a source that is not Naruto's. It's still not his.
At least when you're borrowing power you give something back, but Naruto's basically getting power donated to him cause he has nothing of value to give to Kurama.