Finally received a reply from HCS regarding MyHonda+ subscription dates, see the reply below.
The information you have been provided with is correct, the ‘core connectivity’ subscription is available and valid for a longer period of time as opposed to the ‘Safety & Journey’ subscription. I have been advised this is the length of the subscription service, however I am unable to comment or advise the specific reasons for this.
I am not sure they fully understood my question, so I have sent the following reply.
Why does the MyHonda+ 'Core Connectivity' and 'Safety & Journey' subscriptions start on 18th August 2020 (registration date) and not 29th September 2020 (app activation) or 21st September 2020 (TCU activation date)?
I had also complained about the number of visits I had to make to my dealership to get the TCU set to normal (on), have been offered £150 dealership credit as an apology. It can be used for servicing, accessories or repairs.
So it does go to show it's worthwhile perserving.