What my post said is that they performed similarly in the Championship albeit in different ways. Grealish was the more efficient dribbler, although attempted fewer as you can see by the success rate and number of fouls he received greater than Benrahma. Benrahma's key passes were superior to Grealish's but the output was similar based on the fact that his had a larger number from set pieces. Benrahma benefited from pens in this past season while Grealish did not have any.
The point wasn't to say who was superior or inferior (apart from specific facts), but to say they were similar players when playing at a similar level and would be cheaper.
They would be bought as depth pieces so whether Grealish is more of a midfielder compared to Benrahma doesn't make too much difference because a number of our players are quite versatile and could easily slot in each others' positions. For example, Grealish could play as a 10 or on the left wing. Pogba could play a deeper role like right now, or be the most advanced player in a midfield 3, thus covering for Bruno.
Benrahma could cover for Bruno in that he's quite clearly more aggressive than Grealish hence the higher end product, more attempts at doing things (I should have included his shooting attempt numbers) like attempted dribbles.
In the same reason why DVB isn't exactly like Grealish, but no distinction is made in exact style, so to did I bring up Benrahma. We simply need more bodies in general that could be of a certain quality. It doesn't matter too much in terms of playing style, as opposed to quality above the level of Daniel James, Pereira, etc... Note how James and Pereira aren't the same players either. If they were of higher quality we wouldn't be having this same kind of discussion.