I believe they are both trading and gambling, but since you are betting, they can also be classified as a casino; and about the possibility of adding games that will defeat their purpose as a trading casino, but why not if there are demands and they want to go further it's possible.
Well, if the business can make a profit by adding other games, then it is not bad. I know a lot of platforms started with only one game, but later they added a lot of games, like building their own in-house games and adding third-party games. They did it because their community asked to add 3rd party games and various kinds of games. I am not going to mention any names, of course.
But since Bitwinup introduces itself as an ultimate crypto trading arena, we shouldn't expect them to add other games if they do not announce anything like that. To be honest, this is the first trading website I have seen with such UI.