Symbol versioning doesn't help there unless your applications explicitly state which versions
of symbols they use (which none do because it's so annoying).
Instead they implicitly rely on a GNU extension whereby a symbol with a @@ between name and
version (rather than a single @) becomes the default version and is used if none is specified.
This is invariably the latest symbol version available for that library. So you don't gain
backcompat: what you gain is forward-compat (until you relink, anyway).