Upon further investigation, I think it has to do with the size of the brush.
The bigger the brush the more blending?
The smaller the brush the more blocky lines you get?
So you need to rely on the smoothing tool to get a better blend ( which is weird because in that video he doesn’t need to )
I still don’t think this is intended, sometimes it’s very hard to smooth how you want to.
Here is the smoothing tool in action ( I just quickly downloaded a texture to see it better ) -
Left side is without smoothing.
Going to mark this as a solution, but if anyone could give more information that would be nice.