The water will definitely run into your bathroom.
I’ll have to disagree and ask: Why should it? For the water to run over the shower drain, more water must come from the showerhead than the drain can handle.
This either happens because of a clog in the drain, or it is not properly chosen.
I actually can’t imagine the latter, as long as it’s a normal shower and not a car wash.
I find it unusual, but I don’t really see any reason why it shouldn’t work.
With your argument, it would mean that water would always stand at the drain on the wall. But it doesn’t.