Thanks for clearly stating what I was trying to express somewhat sloppily. This is largely why in discussions of rheology (for rocks at least), talking about them as either "solid" or "fluid" is uncommon and instead you tend to see them described just as "materials", i.e., when texts introduce useful analogues for thinking about the stress-strain or stress-strain rate relationship (i.e., the various combinations of a sliding frictional block, spring, or dashpot that would produce some sort of equivalent stress-strain or stress-strain rate response) they tend to do so in terms of just materials, e.g., "Maxwell materials" or "Voigt materials" etc. Not all geology texts are good about this though.