Before this hypothesis can be tested you'd need to find a personality test with a demonstrable positive correlation to sun signs.

Nobody has succeeded in demonstrating such a correlation. Which doesn't mean that it isn't there. Or that your theory is not true. But it means that any possible effect likely is very small, and we lack the data we'd need to study it directly.

Incidentally other correlations are known between personality and "soft factors". Some are believed to come from similar mechanisms to what you theorize. For instance birth order and body type have correlations to personality.