Unlocked iPhone & Apple iPhone Payment Plan

I want upgrading my iPhone and plan on purchasing it through the Apple store on there Apple iPhone Payment Plan, NOT through AT&T Installment Plan, so the iPhone will be unlock.

I was told that regardless if I’m making payments through Apple, AT&T will still lock my iPhone until the payments is paid in full. Is this information correct? AT&T will still lock my iPhone regardless of who I’m making payments through?

Here’s what it says on Apple’s website: