Yes but a rule of thumb that makes it "seem" flawed might not reflect reality. I gather that they were of the opinion that those rules of thumb weren't helping the industry, in the light of newer, more efficient HPs and better weather comp. So they did some calculations and used their office as a test to verify.
And it's pretty encouraging, right? With some cavity fill and better loft insulation, they'd reduce the energy needed and nudge the SCOP perhaps into the mid-3s. All with no new pipework nor rads.