Adding a suitable version symbol can only help, it can't break
anything. If it's there the debugger can use it. If not you can keep
doing what you already do, and it seems you really need it even for
the normal native cases.
You'll never get them to document interface changes in pthreads'
internal data structures. You're welcome to try if you like pain more
than I do. The only layer the glibc folks support for accessing this
data is thread_db.
Does the current thread-db code at least sanity check version match
internally?