I certainly don't know all cases. But I do know a lot about Macs and RAM. I stand by my statement that if the Mac could run without issue at faster speeds, they would have shipped it that way. There are no hidden capabilities to run faster than specified built into any Mac shipped to date.
My general advice is "don't pay extra for faster RAM -- your Mac will not be able too use the extra speed".
Some of the readouts you get on your Mac are reporting only what the RAMs self-report as their ROM-specified TOP speed. It takes a lot more work to determine if they are actually running at the speed they self-report. You may be fooling yourself into thinking they are faster.
Some RAMs can do proper gear-shifting to run at slower than their specified speeds. There are too many reports from folks who installed RAM with a faster nominal speed, only to find their Mac became flaky because the particular RAMs they installed could not downshift properly and run at the Mac's Bus speed.