Rather like your car, if you drive and maintain it as suggested in the maker's manual you will get the best performance.
Heat pumps are manufactured and tested to national standards and their performance capabilities are well proven. However, as the report confirms, if applied, installed, maintained or used incorrectly the performance can be impaired. Industry is funding these trials and many predicted the early findings of this, as yet inconclusive study. It does already show that heat pumps correctly applied etc will achieve impressive results.