I am quite sure I saw this UC Browser in the App Store, though I have not used it.
Oh, it's in the app store. I mean on the official UC Browser website itself, they don't list Windows 8/RT as a supported OS/platform at all, so by all rights it shouldn't be in the app store. It's either a hack job or the official UC Browser folks decided to keep mum about it.
It seems that Microsoft's addition of a "touch" token to the IE11 user agent string is what's different between IE10 in Win8 and IE11 in Win8.1, so the website authors do need to catch up with the fact that there are full-OS (or at least full web browsers) on touchscreen devices these days. Until then, everyone will blame Internet Explorer, what with its rather tarnished history.