Can't add new phone to xfinity mobile line because it's "not supported"

I just started using Xfinity Mobile a couple of days ago, trialing a 10gb By the Gig plan to see if it'd be an option for my whole family (4 lines). I initially only switched my youngest son's phone (iPhone 8) over to test the connection in our area, and today I decided to add my daughter to the plan to see how that goes. Last time I was at an Xfinity location I was told her old Samsung S5 "wasn't supported", which is what I expected because it's an old phone. I decided to get her a new phone (unlocked), and in order to see what's supported, I went onto xfinity.com/mobile/shop and I found the Moto G Power. Although nowhere could I find it explicitly saying it was "supported" I assumed Xfinity wouldn't be selling "unsupported" phones to new customers. I ordered the 2021 Moto G Power on amazon as it had one-day shipping, and it was the same phone as what was on the website (identical specs).

Now thinking everything was going to go smoothly, I tried to get my daughter onto the phone plan with her new phone, but I was told by the person at our local Xfinity location after they typed in the phone's IMEI that it "wasn't supported".

This shocked me. How could it not be supported? Before going to the Xfinity place, my daughter even tried my son's Xfinity Mobile sim card in her Moto G Power to see if it'd work, and it did!

So if the sim card works in her phone, and the Moto G Power is on Xfinity's website, why the heck isn't it "supported"? I don't need your support I just need you to give me another sim card so I can get my daughter's phone working, which I know for a fact it will. 

So why isn't it supported, despite what I've told you? Well, I think I know why! It's because I didn't buy it from you directly, and because it's not a high-end expensive phone from Apple, or Samsung, or Google.

When I am on your website it is clear to me that your motive is to sell phones directly (to get a cut of the sales?) or to make the customer think they need a 500$+ phone to use your service because otherwise it won't be "supported". You can tell this is what they're doing because when you go onto xfinity.com/mobile/byod/compatibility/device, they only allow you to either select the high-end phones from Apple, Samsung, and Google, or to buy a new phone from them. 

I know for a FACT my daughter's 2021 Moto G Power does in fact work with Xfinity Mobile, as I did a cellular speed test on her phone using her brother's sim card!

Make the problem, sell the solution, that's what you guys are trying to do here and I don't need you to convince me otherwise, I just need the problem to be fixed. How can I get a sim card and add my daughter's new Moto G Power onto our Xfinity Mobile plan? I don't want to hear "it's not supported", buy this new 500$+ new phone from us to fix the problem.