You're still only talking about a 3% difference. Outside the margin of error for a properly-controlled test - which I don't think this is - to be sure. But small enough that if I went into the BIOS of your PC while you weren't looking and down-clocked the RAM to achieve the same effect you wouldn't notice unless you ran a benchmark.

The number of cores is irrelevant to the measure of single core performance. It is entirely possible that single core performance is less for many reasons up to and including silicon lottery.

Raw performance is also not the only relevant metric. Given that these results are within run to run variance there are other factors to consider such as power consumption.

So yes, this is not at all a shocking revelation to me.