Michael Coslo wrote:
While looking for a way to get a little more bandwidth out of an 80
meter antenna, I mocked up an antenna in EZNEC that was thick. I plan on
making an antenna with spreaders and run 4 wires on each leg of the
dipole.

I emulated this in EZNEC by simply making the wire thickness quite
thick, ranging from 4 inches to a foot.

The interesting thing was that as the thickness increased, the antenna
length decreased for min VSWR.

Is this a real thing?

yes.

It's often explained as "extra capacitance from the bigger size", but I
think that's not what's really going on.