Possibly one shared with sleep effects, because goddamn...
The changes to sleep effects (physical/magical sleep protection, startled awake at 50%HP) were implemented due to the sheer obnoxiousness of incapacitating your target, bleeding them out, healing up, beating them down more, lather rinse repeat.
How is spinebreaker+drink blood any different? Its in many ways WAY worse than simple sleep effects, because at least they have beatable saves and if you're slept you can still call for help. Hell... spinebreaker doesnt even seem to use SvPara.