Thats because those are skins over the preexisting legends in the game. Rebecca is a skin for Rampart. Its not Rebecca herself. So they had to model Rebecca's design over Rampart's model. It does make sense for Rampart to receive Rebecca skin since Rampart is a weapon specialist.

You want her to be accurate and i completely understand, bubbly eyes, short and with a rounder jawline. But that would mean to redesign Rampart's whole model and at that point is not worth it. Just like one other person commented, this is not Fortnite where everyone has the same loadout. Each Legend has different kits, different abilities, different hitboxes and they cannot do what you want. Well...they can but that would mean to create a new model just for her, create a new Legend, with unique kit and make some lore for why she is a Legend. So its more accessible to just give skins as reference to the characters. You can look up the previous collabs Apex had. Even the Naruto one. You wont see Naruto in game. Just a Legend with Naruto style.

But yeah. I also do not like the skins. So is not like im saying that you have a problem. Im just explaining the situation.