While I would never disagree with the verdict VBHs perfectly (at the time) formed bottom, there are benefits to using higher octane fuel. My manual states that you should not use fuel with less than 95 RON, to my mind this is not a statement that the engine is mapped for 95, but that the knock limiting function of the ECU will not work well below 95 RON.
The Bosch ME7.1.1 manual states as much: "In principal, the comprehensive dependency of internal torque on cylinder charge, engine speed, Lambda, ignition timing and cylinder individual fuel cut-off could be described in a five dimension map. The decisive step to simplify this dependency is the introduction of two central reference values:
•the optimal spark advance „sa_opt“ and
•the corresponding optimal internal torque „tqi_opt“,which reaches it’s maximum value at optimal spark advance. In some operating points the optimal spark advance is a theoretical value, because of the engine knock limit.
In short, an engine creates maximum torque at optimal ignition advance. That advance is governed by a map which is almost certainly optimised for more than 95 RON (otherwise this would be the maximum, not the minimum) and the ECU retards the ignition timing back from optimal based on the input from the knock sensors. While VBHs **** and a dyno run in a hot environment (a hot inlet charge also lowers the knock limit) may have not shown a measurable improvement, this doesn't mean there isn't one in my opinion.