Yes, multiple data points for the same thing. Exactly. It's to get a better measure on that thing (problem solving / coding).

There are absolutely people who "learn" dozens or hundreds of problems and then still don't get a job. That's actually a good signal about the interview process. Preparation shouldn't land a bad engineer any ol' job they want.

Unfortunately, it sometimes does -- and that can happen when a company asks easy or well known problems. Far too many companies do that.