Apple Upgrade Program as a T-Mobile customer

I have a question on the Apple Upgrade Program.

I am into Year 1 of the program - originally as an AT&T subscriber and recently switched over to T-Mobile a few months back.

As a T-Mobile subscriber, my question is whether I can pre-order the newest iPhone model (iPhone X, in my case) via the Apple site on Day 1. Having T-Mobile is tricky, as I can see that IF I was enrolling for the 1st time, Apple tells you to visit an Apple Store and check in with a Specialist - essentially eliminating the ability to pre-order online on Day 1.

AT&T, Verizon and Sprint skips this step of visiting a store - you can do it online. (From what I gathered online and unconfirmed, it is T-Mobile's billing system that forces T-Mobile's customers to do this.)

My question is: What if I am already enrolled in the Apple Upgrade Program, do I still have to go to the store to pre-order a new iPhone - as a T-Mobile customer?

I would like to clarify this "activation" or enrolling (the wording can be confusing). Is it activating the iPhone or activating the plan that requires me to go visit a store? I would like to know so I don't waste my time trying to pre-order this at 3AM EST on 10/27/17- I need my sleep, as an East Coast citizen in the US!

Thanks.