For hydraulic power discussion see
this most excellent thread
Basically it's just flow rate * pressure drop * a conversion to get to a final unit of "W". The beauty is that it combines the ease of comprehension of dT vs flow graphs with the necessity to include dP vs flow info to be predictive.
And we never said it was a low flow block or that low flow was ever desireable. I suggest that you complain to the "experts" who did.