It is a commercial arrangement - Wingly is acting as an AGENT for the PPL - Wingly are getting paid from the deal somewhere so this is not cost sharing between a PPL and a friend etc
In addition, which, for me, is the coup de gras ....... Wingly are actually selling the public gift vouchers for a flight with a PPL - a flight yet to be organised !!
If you have an AOC you face the prospect of being taken out by PPLs flying transport flights.