Mr Smith.
the pilot was using radio alerted see and avoid. Remember that was the one that the old BASI loved so much.
Alerted 'see and avoid' is a heck of a lot
better than unalerted 'see and avoid', but it does
not guarantee that paint will not be swapped, or britches filled.
Now why would anyone make airspace E rather than G ?
As I see it, it is because the traffic warrants an increase in protection to IFRs, but
unsurveilled E is effectively the same as G, except that the risk to IFR has increased.