Update: Microsoft has now sent WinBeta this statement:
"Last week's Lumia 950 and Lumia 950 XL phones announcements generated huge interest. We made some prototype devices available for a limited time in our retail stores, so that customers could get an early look at our best Windows experience with Windows 10, on our most productive smartphones ever. We've now removed the prototypes from the stores as we finalize the experience, and look forward to rolling the phones out next month."
WinBeta reports that the decision was made because there is an unspecified hardware issue with these prototype devices. It's definitely not uncommon to encounter problems when using pre-production hardware units, so this news should not be misconstrued as a problem with the Lumia 950 XL itself.
There's no word yet on when the demo units will be returned to those stores. This issue apparently only affects the Lumia 950 XL; Microsoft Stores stil have demo units of the Lumia 950, the Surface Pro 4 and the Surface Book.
Source: WinBeta
