If the military can make electronics that are immune to vibration so can the high end audio industry.Yup! One of the ways the military does it is vibration mitigation solutions- for example EAR makes a bituminous based extensional damping compound that gets used in submarines. When tubes were involved they used isomeric mountings on the tubes sockets to limit vibration transmission to the tubes themselves.
BTW 6922s tend to be more microphonic than the 12Axx family of tubes since they were intended for instrumentation rather than audio. That you have a set that is so low in microphonics that you can't hear it when tapping on them is really unusual- so much that its in the realm of outright miracle.