I don't know about this Apex stuff, but my thought is you are bringing another potential tackler into the box where we are trying to run and NO ONE DESIGNED TO BLOCK HIM!!! Even if he doesn't make the tackle, its another body inside the box (insert obligatory "your mom" joke here) to navigate around.
The "spread" is so successful not because of magic plays or anything else, its 4 wide for a reason and gets defenders defending the whole field. So let's do something different. Let's bunch everyone up and run inside/outside zone into 20 bodies. We have a 53 yard wide field, so lets play football inside of a phone booth.
Now passing from a bunch formation is cool because the defense has a harder time reading the routes but it does leave you open for a wacky blitz scheme because everyone starts in close.
When I coached, when a slot went in motion, I would roll the FS down to the motion guy and either roll the original cb back to the FS spot or he would follow (giving the QB the impression of man coverage), and then blitz him off the edge, which turns the coverage to zero (man). Doing this overloads one side and screws up their presnap read and who the RB is supposed to pick up.
On pass blocking plays, with 5 linemen, a QB, a RB, there is typically 6 defenders. Whichever side the RB is going (play action pass), the RB, G, and T on that side have the DT, DE, and LB to that side. The opposite side, the C, G, and T have the DT, DE, and LB to that side. Either side the CB came from, screwed up their scheme.
What do we do? We have the CB run back and forth following the motion like a lost puppy, often trailing, so if they give it to the motion, he has a 5 yard running head start.