You are absolutely right.

Bosses care less about what stress their employee is expereincing. But they have to care about their own career development. Not sure if this is true everywhere, but in my company people manager have year-end review on people management skill. If employees are not happy, they will skip level to complain, even worse they may quit ( in this economy, managers have some leverage). If there are too many complaints about one person or the turn-over rate is high, there are some problems with this manager. So at some level, they care about complaints. Hopefully this is the case in LZ's company too.