Yep, both erroneous readings have been there for as long as Windows 7 and DX11 cards have been around.
The reading from dxdiag is fixed in SP1 when it comes out, but the one that shows DX10 from the WEI is still there, even with using SP1 RC. I don't think MS ever knew about that erroneous reading, only the one from dxdiag. If they have seen the wrong reading with the WEI and are going to fix that too, I've never seen any evidence of it.
This used to say 10.1 until they released the hotfix for it back one year ago here
. Same is in SP1 now.
Correct reading now with using SP1 RC. The system tab there showing DX 11 is just telling you Windows 7 is DX11 capable, it's not a reading from your card. The DDI version under the Display tab is where you want to see the 11.
Nothing to worry about though, it's just a incorrect report, doesn't affect anything.