On Saturday, 8 December 2018 12:25:35 UTC+2, wrote:
“Do these "phantom" classes give more FAI ranking points to pilots (4 winners instead of 2)? I dont see any other reason for this. “

No.

Reading FAI ranking rules it sure does. Pilot quality factor, competition rating all are based on number of good pilots in same class. Put same pilots to multiple classes and you have very good phantom competition that gives a lot of ranking points. Very clever.