He said that the engines weren't running the higher oil limit and the FIA allowed them to run the higher limit anyway. So...
Now, I do agree with the above statement, however, that isn't to say the engine is designed to work best with a lower oil burn limit... it just happens to be able to withstand the extra force of combustion with the higher oil burn limit (for a short period). You only have to hear the team radio to realise that Merc can't run in that engine mode for extended periods. I can't prove it but I suspect other teams (Ferrari) began investigating the extra horsepower that comes with oil burning and found engines dying. Perhaps they were happy that the limit was dropped as it reduced the Merc quali advantage, or perhaps they were gutted they couldn't ride on the bandwagon.