I am really pretty sure the techniques were the training tools for developing the power.
Maybe my answer is pointless.
As I said, I don't know what every teacher ever did or does and I've never done the rowing exercise although I think it is one of those +.
Tomiki has a set of solo-exercises and also paired exercises which are done in every bloody lesson. And I can relate every move in his kata to those sets. And that's not because I am such a genius but because I was taught to do that.