It's called the Kalashnikov variation of the Sicilian and it's not only fine but one of the sharper variations for black. I don't know what the above post is about but the main line after 5. Nb5 is 5. ... d6. The only real difficulty is if white opts for 6. c4 going for the Maróczy bind and even then it's perfectly playable.
Why is 4.e5 a bad move in the open Sicilian?
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"what gives black such a disadvantage with 4.e5?"
++ The backward pawn at d6 and the hole at d5 where a white knight can install itself.
"What positional advantage does white have in order to force a win from the 4th move?"
++ The weak square d5, but if that is enough to win is questionable. The engine is weak in the opening as there are too many possibilities to calculate for a meaningful evaluation within the calculation horizon.
The open Sicilian is quite popular, both the 2.d6 and 2.nc6 line, but if you put 4:e5 in the engine, the engine says white has a 1 point advantage and will force a win with best play. what gives black such a disadvantage with 4.e5? What positional advantage does white have in order to force a win from the 4th move?