chess is never easy.
But you should say in which of the variants I gave above, and at which move white plays 0-0-0.
In the variant 1.d4 Nf6, 2.g4 Nxg4, 3.e4 d5, 4.Be2 h5, 5.h3 Nh6, 6.e5 Nf5!, 7.Bxh5 c5,
white still needs two more moves (Qd(e)2 and Nc3) before he can play 0-0-0. Time which Black will exploit to organize a further counterplay over the c-file (in addition to the pressure in the center).
lyde Nakamura
schlechter55
I wouldn't say the advantage for Black is 'very slight', after 1.d4 Nf6, 2.g4 Nxg4, 3.e4 d5, 4.Be2. Black can play 4....Qd7 (5.exd5 Qxd5), or 4....h5 (5.h3 Nh6, 6.e5 Nf5!, 7.Bxh5 c5, white has lost his lead in development, he is left with weaknesses on the kingside, and his center scrumbles).
It is not that easy as you say. White just castles queenside. I know that
the White kingside pawns are scattered and that is why any sane
player who plays the White side would castle kingside. I took down
Reynolds Takata 2100 and Victor Tsoy 2200 with this gambit some
years ago. And also Cornelius Rubsamen 2 times in tournament. Rubsamen
and Takata went on to become US national masters.
Best Regards
DarthMusashi