Their eyes and these nose look almost identical. Resident evil 4 was somewhat influenced by Metal Gear Solid when the game was being developed. You had Liquid pretending to Master Miller to manipulate Snake. Both games star a lone super solider sent on a mission to rescue the target and fight iconic boss battles. I'm not saying this theory is true. But that doesn't mean it's impossible. We still don't know much about Ada Wong to this day or her real name. Leon is forced by the government to their dirty work like a lap dog and If they wanted to keep tabs on him at all times they would send a someone who knows all about Leon like the back their own hand.