Now that foundation for WinP is same as for Win, one can reasonably expect that stuff not related to graphic API, should work on both incarnations of IE.
(Win8 gpu drivers support “full” range of requirements, WinP8 gpu drivers may be tailored for mobile GPU’s)
And as anybody can see, MS is still fighting tooth and nail to get IE up to modern state equal to other major web browsers. (Despite what you hear from MS PR each time they release IE ;) )