You're arguing that they are substitute assets for each other that might move reciprocally, like stocks and bonds are. But equity at seed stage and public stage

You're arguing that they are substitute assets for each other that might move reciprocally, like stocks and bonds are. But equity at seed stage and public stage are the same asset class at different levels and move more in tandem. My argument was more about the wealth effect though, which is that a crash in stocks makes Angels poorer and thus less likely to invest in risky startups.