ok and if white takes the pawn?
4...e5 5.Nxe5 and 5.dxe5 Ng4 6.Bg5 and black is busted...
This is not king's indian attack though, it is fianchetto system vs king's indian defence, where black can prepare e5 with d6-Nbd7-e5.
KIA is defined with d3 and e4 at some point, not with d4.
I get these kind of positions fairly frequently. When white doesn't take the e5 pawn, black gets into a favorable reveresed French Structure.,