Replace[{{x^2, Sqrt[x]}, {x + 1, x - 3}}, f_[x__] -> f, 1]
Level 1 of Replace works here as expected with output {List,List}
Replace[{{x^2, Sqrt[x]}, {x + 1, x - 3}}, f_[x__] -> f, 2]
But with level 2 I would expect something like {{Power,Power},{Plus,Plus}}. However, the output still is {List,List}. Why?