This is a lie, how can I lose more playing alone? I prefer playing any games alone, either on home consoles or even mobile games, do you know that not all games have two players available ?
You will only need someone next to you if the game you are playing requires two players or two player option is available, what are you going to be doing? Talking with someone while you are gambling? You will be distracted.
If you want someone to stop you from gambling overtime it's your problem, your type of person shouldn't be gambling online at all because you can't control yourself.
I agree with you on that, playing alone doesn't influence the game in anyway, it's either you win or you end up losing and it has nothing to do with gambling next to someone else. The problem with a lot of gamblers is that they assume to have a way around gambling but there's nothing that can make you be in profit consistently especially when it comes to playing crash games. Just as you said, if he needs someone to always put him in check then he should not be gambling because he has no self control.