I looked at the line and it seems Stockfish wants to push the e pawn after white reacts with Rb1. Then e4 and if Nxe4 Nxe4 Qxe4 then Bg5 wins. So e4 forces white to move back the queen. I guess it also cuts off the defence of f5 by the queen. And somehow it ends on a draw by repetition if we follow all the moves by Stockfish.
However it seems there should be many other lines playable and if white does not fall for the trap, then it is equal but not so pleasant to play with black compared to Qa5 which at least tries to gain some space.