>>532676147
As far as I know it makes it likelier to inherit skills but it doesn't affect the floor or cieling of what you get, so it's still entirely RNG.
Never seen any actual math on it, but based on personal and second hand experience (so, a collective amount of thousands of runs) it's meaningful enough to be worth going for, at least. Not worth using considerably worse Umas just because they have higher affinities, though.