I think (and hope!) you're right. I run all mine on super unleaded anyway, it improves the economy and the power but not both at the same time!
I also run my lawnmower on it which might seem like a waste to some. Some years back i did a test using Tesco unleaded, BP unleaded and BP Ultimate.
I had a fairly large garden then so it was a good comparison, starting with a full tank on the lawnmower i had to refill at least twice on Tesco fuel, once on BP unleaded but it was on vapour by the time i finished and on the Ultimate i was only filling the tank completely twice for every 3 cuts of the grass.
Bit of an anecdotal test i'll grant you but i did have repeatability with it after i moved and have a smaller garden.