Hmm, this is a strange one indeed! The floppy image you sent me contains the exact same files as PoP v1.0, except for the main Prince.exe, which is a different size. And yes, this is in English and it does say v1.1 inside the game. If the file size had been same, I'd have done a bitwise comparison and maybe figured out whether someone hex edited v1.0 as a joke to make it look like the fabled long-lost v1.1, but since the sizes are different, can't easily compare. This Prince.exe doesn't match those for v1.3 and v1.4 either, and the German v1.1 EXE is different as well. So either someone has changed an existing EXE a lot, or this could very well be an authentic copy of PoP v1.1.
Honestly, I can't say. Nothing is known of this version, since it has never been seen by the public AFAIK. I always thought v1.1 and v1.2 might have simply been internal test releases before v1.3 was released officially (and finally v1.4 years later for the Collector's Edition on CD). So if this is indeed v1.1 and there's also a v1.2 floating around somewhere (you have that too by any chance?

BTW, I played PoP v1.0 and v1.1 a lot after downloading the latter and frankly, couldn't find any difference. If anything, it must have minor bug fixes or something, which is why I guess it was never deemed worth of a public release. If anyone else wants to compare them, you can get v1.1 here or here. I simply extracted the original floppy disk image and made an RAR since not many people may know how to deal with such files anymore. If anyone finds any difference between PoP v1.0 and v1.1, or more information about the latter, do post here.