I’m not sure what may be out of date with my answer.
Your experience shows that every insurance company will use different criteria at different times so any driver may not be quoted by one company or given a ridiculous quote whilst a rival will give them a good quote.
Whilst not every company will act on a letter from RSA many will and I fail to see how it would actually hinder you. At the very least, it would explain the gap in your insurance record.
As the OP will hopefully enjoy hassle free motoring with MB for many years to come, who knows what the future holds and my response to him was to put his mind at ease.
Moss