I know Gary & Joe personally; they were college lecturers before they went off to form efixx with Gordon.
I have lost touch with Gary since they started efxix, so I don't know if he is still teaching or not.
He does know his onions, but he doesn't know everything.
In that video, it is said more than once that there are other ways of calculating diversity, and it is giving an example of the method shown in the OSG.
The IET themselves publish 3 separate ways of calculating diversity.
The OSG method, the method in the design guide, and the method in the commentary book.
All 3 give different values.
The narrator of the video states that the OSG method just gives a general idea of the demand and says, "a form of diversity", acknowledging that there are other methods, it would seem.
Personally, I would like to know where the extra 12.8 A of load comes from when you just change the board.
If fixed appliances or circuits are added, then I can see a chance for an increase in diversified load.
In this situation, you have removed the storage heaters, so the load on the installation overall should reduce.
The method in the video is also that on page 138 of the OSG Appendix A, table A2, point 9, "Standard arrangement of final circuits in accordance with Appendix H".
If we then go to Appendix H, we find that the sizes of breakers, the configuration of circuits, the cable size, the circuit protective devices, and other things are specified. If the installation in the premises does not comply fully with the design criteria in Appendix H, then the method of diversity in the video cannot be used. In the video it states that the method is for standard circuits as per Appendix H.
So to use the method in Appendix A indent 9 the requirements of Appendix H need to be met.
I had a meeting just last week with the senior engineer at British Gas new technologies, so EV charging, solar panels, battery storage etc.
The topic being diversity in domestic premises.
The outcome of their assessments, when comparing measurements with the various IET calculations.
The result of the calculations gave values well in excess of those measured at the properties.
The measurements went on for weeks, not hours, to ascertain the load profile.
I don't particularly think anyone is "wrong", but many of the methods of calculating diversity give values much greater than those experienced in real life.
Look at the comment on the video by the ex-DNO engineer.
I have been told the same by one of my local DNO engineers, and I don't mean one of the "engineers" who does overhead or underground cable repairs. I mean, one of the engineers who works in the office designing the network.
The engineer I spoke to (many times), told me that they used 40% of the allowed load, or the fuse rating in the cut-out, but they weren't bothered if the fuse was 60, 80 or 100A, so they could allow anywhere from 24 to 40 A per house, & they weren't bothered if the fuse was updated after connection, so you could have a house with a 24 A allowance and a100 A fuse.
The allowed load would come from a connection request form provided by the customer, probably completed by the installation designer.
Personally, I wouldn't worry about the load, as I don't believe that the fuse rating would ever be met.
p.s. One thing I had forgotten about is the proliferation of LED lighting. I bet a house full of LED lighting is MUCH less than 6 A, let alone 40% of 6A per circuit. Some properties will have multiple lighting circuits, I have 5 at home in my bungalow.
Look at the W per point in OSG Appendix A, especially that for lighting.
