Okay, for the life of me, I cannot find any indication in the link the article provided that T-Mobile is offering the $200 rebate for anything other than the iPhone X. The only deal it's showing regarding other phones is a buy one get one (iPhone 8) free deal. Am I missing something?
Okay, I asked the article author about this, sounds like the article is probably correct:
I wondered this myself, but I went off T-Mobile's press release, which they emailed to us. Here's what they said: "First, starting February 23, 2018 and for a limited time, get $200 back via a Prepaid MasterCard PLUS the value of your trade-in phone when you purchase an iPhone X, 8, 8 Plus, 7 or 7 Plus."
I'm not sure why the website only focuses on the iPhone X, it makes it a bit difficult to corroborate the information. But I asked and that's what they told me.
I did confirm through other media sources that the above, and the article, are correct. HOWEVER, I also realized something that I hadn't noticed the MR article: you have to trade in your old "flagship" phone, it's not optional. Still a solid deal, I think, but I had previously been considering just forgoing the trade-in and selling my wife's Galaxy S7 on Craigslist for more than the trade-in value (roughly $58).