Yes, there is a difference between metric and standard primers, but it's only about .0015". There is more difference with the hardness of the coil stock they punched the primer cups out of.
We see the same thing with our domestic primers with Federal small pistol being the softest and CCIs being probably the hardest one.
All metric primer cups are not as hard as the PMC and Tulla primers are.
I have a 12k case of Fiocchi primers that are .0015" larger than my Winchester small pistol primers are and they seat easier than the Winchesters do in my domestic brass.
I consider them the "Federal of the European primers". They run really well through my LNL-AP press, and my antique Lee Auto Prime ll that runs on top of my RockChucker. They burn clean, always go bang, and punch out easily without sticking to my punch pin.
There is nothing not to like about them that I have found, except that I can't buy anymore of them.