Be sure you are clear with specific statements like this. The uninformed will read it and then it becomes the only fact they know, and they repeat it, and it becomes gospel down the road. . Rounds start to drop yes, but will be completely affected by your zero distance, grain weight, and projectile speed. 115gr round at 50 will not be the same as 147gr round. A 2" barrel versus an 8" barrel will also change this.I sight almost all my handguns in at 25 yards. there is very little "rise" at shorter distances so you can hold dead on up to 25 yards. After 25 yards a 9mm starts to drop. At 50 yards you're about 1.5 inches low and then it gets worse from there.
Scott Jedlinski, the red dot dude, teaches a 10 yard zero for red dots on pistols. Great class, highly recommended.
Here is his explanation.