Highball boulders are pretty unsafe if you fall near the top. This is why climbers will top rope to figure out all the moves first. This might be true of short outdoor boulders as well just to save effort.
Then there are multi story bouldering walls where you fall onto a ramp. This type of wall will be taller than some rope walls.
Yeah that’s why I wonder if there are regional differences. E.g sport vs lead climbing.