Hard in "hard science" doesn't mean hard as in difficulty, it means hard as in not soft. Soft sciences are difficult to explore since they aren't rigid, they move around as you prod at them etc, you can't get a good grasp of its shape since they are so soft.

Physics on the other hand is hard as in unyielding. It is easy to figure out boundaries of physics and map out what is and isn't true, and the few cases were we made a mistake everyone can agree a mistake was made and that formulas needs to be updated since physics is so extremely hard that even a tiny error will get noticed.

Hope that clears it up, physics isn't hard as in difficult, its hard as in rigid. And psychology is soft, not easy.

So, your statement doesn't make sense at all in this discussion, they just said psychology has soft traits, and then you say "ok, so its hard since its soft!". No, soft is difficult, not hard.

So for example, physics is like describing the shape of a metal spoon, and psychology is like describing the shape of a pillow. You can see how describing the shape of the pillow is massively more difficult, because its not fixed, so you have to come up with a language to describe all the ways it can deform and how that would work.