I think it means no more than what always appeared on the "supported phones" page: (sorry can't link as my post count isn't high enough)
If your phone isn't listed, and no preview builds appear under Enroll in the Windows Insider app, then your phone isn't supported and it may or may not be supported in the future.
In other words, just because WP10TP got pushed out to unsupported phones by accident, it doesn't change their plans, they're not suddenly now going to start supporting WP10TP on those phones.
That said, we were told previously the main reason the HTC 8X wasn't supported at that time was because Microsoft did not have the recovery file from HTC. If they get it as a result of last week's screwup it can only help our situation.
Aside, I reviewed the Insider Program Terms & Conditions (sorry again, can't link) and after saying:
Microsoft Windows Insider Program terms & condition said:
the Program Services, if installed on a mobile device, may inadvertently damage your device rendering it inoperable.
..it goes on and on at great length to spell out that Microsoft is not liable for any issues that might arise from the use of the previews, and says users can't sue Microsoft or take part in any class action litigation, only individual arbitration. Interestingly though, it only applies if you live in the USA (or if that's your principle place of business). I live in Canada! Ha!
If my phone is not working by Friday, I will request a replacement phone from Microsoft.