The definition of '100hours ' in these ads is often not clarified:
There's a world of difference between someone who got his PPL after 98 hours and has flown 2 hours post PPL and someone who got his PPL at, say, 50 hours and has 50 post PPL hours.
I don't think they usually mean P1 hours, but total hours in which case my argument above applies.
Most groups are flexible however: The group I joined in early 90s was a '100' hours group: They let me join at 70 hours total and did 5 hours with an instructor (it was before retractable and C/s prop sign offs were needed and the group operated a complex single out of a grass strip, so two new skills to learn).
And I'm still with that group..................