I think his point is that if you write normal single threaded code then your other cores are going to be idle. But if you write in a high level JITed GCd langua

I think his point is that if you write normal single threaded code then your other cores are going to be idle. But if you write in a high level JITed GCd language then the other cores will be busy making your main thread run faster by profiling it, recompiling it with risky optimisations, clearing garbage asynchronously and so on.