Device "blocked" by T-Mobile, any experiences?

I purchased an iPad Pro from Swappa that was clean at the time of purchase. I tend to like Swappa. A couple of months later, it turns out the reason this device had a lower price that most others was it was still being paid on in some form. So, while it was clean at the time of purchase, it no longer is. T-Mobile checker and some others report it as "blocked". However, AT&T, Sprint, etc report it as clean. In fact, I have converted the former T-Mobile data plan to Freedompop and it works just fine since it is blocked. My understanding is a stolen device would be blacklisted, which may be different than simply "blocked". Blacklisted (and I don't know anything about those) appears to apply to all domestic carriers. So, if the device was blacklisted, I would assume it would not work on FeeedomPop or any other carrier here in the US?

So, my question is this, does anyone know if T-Mobile blocks expand into blacklisting? I have to decide should I pursue a refund via Paypal. Swappa has refunded fees to me, so, continue to have no issue with them from my point of view. The problem with pursuing a refund is:

[ul]
[li]I would have to return the devivce[/li]
[li]I would need a new device[/li]
[li]I purchased Applecare for the device, which I would likely lose[/li]
[li]I added a very difficult to apply screen protector (on a 12"+ screen, not so easy at least for me). And I'd really hate to do that again, and I would lose that money as well.[/li]
[/ul]
So, it only matters to me if the likelihood of the block turning into a blacklist would be pretty good. As then, I would be unhappy since I need data on it. Yes, I could tether, etc, but, I want data on it.

So, does anyone have any experience or advice in this area of T-Mobile blocks?

How is a block different than a blacklisting?