In my short career, I'd say it's that young startups (or teams) with a higher than average number of females WHO STAY THERE (ie low female co-workers turnover)

In my short career, I'd say it's that young startups (or teams) with a higher than average number of females WHO STAY THERE (ie low female co-workers turnover) that really survive the longest. If female devs/marketing/HR/management escape fast from the company, its a red flag to me.