Ping and ring are VERY closely related. It's the exact same sound (originating from the switch springs), only some switches have a longer sustain than the others. Filcos are very solidly built, so like a good guitar, tend to have a long sustain sometimes :-)
BTW almost all mech keyboards ping to some extent if you try. I get some ping from all my mech keyboards, and a couple of them (one of my Kinesis Advantage and an IBM mini's) ring, ie the ping sound lasts long, so when you type hard, the sound never has a chance to completely die down, producing a ringing effect.