I have switches that are not currently mounted to anything at all in most MX and Gateron variants. If you listen close enough to any of them they do produce a metallic sound since there are metal components - and in some cases I mean putting the switch basically inside your ear in a silent room to hear the spring noise. However, this noise is not the noise that occurs when I consider a board one that pings. I have never heard a switch that notably pings to the point of irritation on it's own. That is not to say it doesn't occur, just that this has not been my experience.
What I do know is that my CODE is difficult for me to type on because that thing pings beyond all reason and there is no shutting it up. I also have a board with MX Blues that did not have any noticeable ping when it was in the original case, however once I switched it to an aluminum case there was very obvious ping. I put some drawer liner in-between the PCB and case and now it is once again, blissfully, ping free. It is that dead space in the case, and sometimes the material of the case itself, that allows for resonance to occur which makes pinging so noticeable. Strong switches could add to this since there is more force involved, certainly.
I would agree that the material and assembly of the plate can make a big difference in the produced sound when typing. I have no first hand experience with KULs, but everything I have heard indicates they do not suffer the same issues as the CODE. I have had boards with MX Blacks, as well as the aforementioned Clears, which have had no ping (again, not the CODE, that thing is a headache in keyboard form). So it is not an issue specific to strong switches.
