I rather doubt it was rendered in HD since they claimed they didn't have the extra footage to put the DE on Blu-ray in2009.
Unless they were flat out lying about the fact they had a readily available master of the DE in HD.
Now it's 4 years later and still no sign of the DE coming to Blu-ray---that sounds unlikely if they had it ready to go.
I can see them being too cheap/lazy to convert the extra footage to HD format, but if it had already
been done I think we would have seen some '30th anniversary TWOK DE" release last year.