When you think about it, there's not much technique to a lot of skills in PS. Metallurgy, for example, is just sticking ore into a furnace and watching it melt. Armour, is just wearing some armour, it doesn't require technique (at least not techniques that increase the protection of the armour). Mining is just chipping away at rocks and trying to extract ore, not much skill there either.
Digging wouldn't be much difference either. It could effect how quickly you can dig down, how far you can dig down, and the chances of destroying whatever you're trying to dig up with your shovel.
Understand?