These are legacy 2D pan pot laws from the original IRCAM Spat library. They only become available when using 2D channel based streams and are primarily included for backwards compatibility.
How does it work?
Angular and PanR are pairwise amplitude panning essentially the same as VBAP 2D described on the next page. There is a subtle difference however, in the way the panning law changes when moving the source from one speaker to another.