The risk of a 100 hour pilot having an accident may be no greater on a Wingly flight than when he is flying alone or with a friend. The issues are
first that it is a further nail in the coffin of small AOC operators, many of whom are also training establishments. It may increase training and competency costs, reduce choice, and hasten the demise of general aviation
second that one day there will be an accident or a tax investigation or something else and as always happens in the UK the result will be to punish and ban. The industry and hobbyists will be hit with restrictions and additional regulations.
I suppose if you have a shiny new PPL, are desperate to fly and have little understanding of GA this seems like a great idea. Time to educate....