Lightroom Mobile is new, and it started on the iPad partly because the iPad is overwhelmingly the most common tablet owned by Lightroom users. If you don't believe that statement, note that 60% of mobile visitors to 3 different Lightroom web sites use iPads, 23% iPhones, and the top Android device, the Galaxy, accounts for just 3%.
It now runs on iPhones and Android phones too, and people have made it run on Android tablets. Your SurfacePro should be able to run real Lightroom.
I'm certain that those marketing factors are correct. However, with the paucity of support for non-Apple devices, would one expect high visitor volumes on non-supported platforms?
Apparently Adobe does want to be an Apple company. That's fine. Android and Kindle HDX users will just have to move elsewhere thereby diminishing the value of the Creative Cloud for Android, Kindle HDX and Windows users like me.
You can browse those sites on any mobile platform, including non-supported ones, and the numbers have been consistent since before Lightroom Mobile was ever announced.
So the statistics probably do represent the mobile platforms actually used by Lightroom users, meaning it's not a desire to be Apple-limited - it's a simple business decision. Why should Adobe prioritise mobile platforms that few Lightroom customers use?