Maybe it's the case for U in the US, but not where I work (France).
This vectoring point (above safe altitude) has nothing to see with the class of airspace. Of course I will never give radar vectors below minimum safe radar altitude.
-As far as IFR are concerned I can give vectors in E airspace as long as I'm above the minimum altitude. And that's kind of stoopid because I don't know if there's VFR traffic or not, but because as someone said as E airspace is controlled, I've the right to do it even if it's not really recommended: how would an IFR pilot know the kind of airspace he's in, if he's under radar vectoring...and then watch out for possible traffic.
- But radar vectors for VFR in E or G airspace above or below (of course) the safe alttitude is not allowed for us. I can only suggest a track to join a point or a heading to avoid a traffic, but only suggest !