If there's a notable difference in skill levels, they wouldn't get the jobs in the first place, would they? After all, everyone wants to work in tech where even the lowest paid employees are usually beating median income by a decent margin. Companies have no incentive to keep low performers around when they can be replaced nearly instantly.
Not necessarily true. Not just women, but many ethnicities get hired for diversity reasons and to balance the ratio of white men vs. women, blacks, Asians, etc.
In the case of a previous employer women who were administrative assistants got promoted to IT supervisor and IT management jobs for diversity reasons.