I see what you did there. I do think the neural spines would sustain damage from moving beyond the normal range of the tail. But since they are almost certainly being held in by skin and connective tissue they would probably heal to some degree most of the time. This was exactly why I didn't straighten out every neural spine perfectly from the fossil condition.
It doesn't seem to do that in Anchiornis, and even in modern (plucked) birds you can see usually see where the pubis ends separate from the pygostyle, despite them being much further retroverted and no longer meeting along the midline so they could swing the guts back there.