Yes,on vacation is the Assistant Manager playing! At least as i know the game is processed same way, SI never said that games are processed on different way during vacation or when you play it.
Big things is if you expect that the tactics impact like previous version (like breaking the game) that's not happening anymore you have to do things during the game.
Example : you getting 3 people with yellow cards you have to change approach like removing stuck-in or even remove tackle harder and even going to "pacifist" solution like to go to "stay on feet"etc.
That's just an example,this was even a bad run,usually from vacation Bournemouth even goes 2/3/4th place pretty easy. And that was with a 424 i am testing out. So imagine