Category-6 parts, including the cabling, plugs, sockets, patch panels, etc. do indeed need to meet the Category-6 requirements. A cable system must use all Category-6 parts, and pass the Category-6 test suite before it can be certified as a Category-6 cable system, despite what may be printed on any or all of the individual parts.
The actual installation plays a very big part in this, and I have seen very good, experienced installers struggle to get a cable installation to pass the Category-6 test suite. Something simple as having the blue wire on top of the blue-white wire when punching down the wires can cause it to fail. I have also never seen an installer able to make a Category-6 patch cord that will pass the Category-6 test suite. As far as I'm concerned, only factory-built patch cords should be used.
Unfortunately, there is a lot of crap sold that claims to be certified for one category or another. I would not be comfortable using any part that claims Category-5e and Category-6 compatibility. The reason is that most Category-5e cable is 24-gauge wire, but most Category-6 cable is made thicker (23-gauge wire) in order to meet the Category-6 requirements. Something seemingly so small can cause big problems.
The only way to be sure that any cable system meets Category-6 is to individually test each cable run with an expensive tester. A cable installer is supposed to do exactly that after installation, repairing any problems, and providing the customer with a complete report of all tested parameters at the end of the installation.
FYI, there really is no such thing as Category-5, anymore. Categories 1, 2, 4, and 5 have all been de-regsitered/de-certified by ANSI/TIA/EIA, the standards bodies responsible for cable categories.
