No, that's well known, and is only half of the rotation. (A rotation of the angle between the electric and magnetic fields.)

This is apparently something new, not sure what though - it's not something I ever learned about with photons.

Not sure that this is new. It is known that channel capacity can be scaled up linearly with the number of receive/transmit antennas by properly de-mixing the signal at the receiver (or pre-coding it properly at the sender).

This is known as MIMO transmission, see https://en.wikipedia.org/wiki/MIMO for details (also has the capacity formula).

What these people call "vortex wave", is just precoding/decoding done in a fixed way using fixed antennas. But with non-line-of sight channels and moving sender/receiver you will need dynamic MIMO coding anyways. This is already implemented in LTE (2 antennas in the handset, 4 at the base station, AFAIR).

That would be my guess too, especially as two crossed yagis are a well known way to receive circular polarized signals:

http://www.qsl.net/dk7zb/Cross-Yagi/crossyagi.htm