I never was asked that from Apple for my TMO phone.T-Mobile here. I needed to enter PIN for T-Mobile line on Apple site. After Checked out from Apple I received a text from
T-Mobile saying “Thank you for eSignature…..”
My 14+ was financed thru Apple Card 2 years ago and it's been paid off.
When I clicked on TMO as my carrier during pre-order, I was never asked anything about my phone#, PIN or verification.