As suggest you try it and run memtst86 on it. You will have to be lucky.
There are a large number of youtube factory video that show how they manufacture and test memory.
If the memory can test faster why wouldn't factory sell it as the faster kit and charge more money. In most cases the memory has been tested and it will not reliably run much faster than the rates the factory put on the package.
It would have to be something like they didn't need any more faster memory kits so they packaged them as slower kits.
Overclocking is pretty much dead now days. The parts that can perform faster have been grabbed by the factory or other people farther up the supply chain. By the time the end consumer get a chance most the really good stuff is long gone.