No. The worsening performance suggests that the pool of women large enough to populate the board seats that the law now requires is less good at doing so then the pool of men they are displacing. Given the limited evidence available, even that statement needs qualifications; however the evidence presented says nothing about why those populations differ.
My not entirely thought out belief is that if the issue is interest, we would expect to see less of a performance drop than if the interest was ability [0].
Actually, if performance continues to degrade, that would likely just be a sign that whatever negative effect is being observed takes more than ~3 months to fully materialize.
[0] Although, even thinking about this for a moment, I can envision a bunch of situations where this would invert.
My not entirely thought out belief is that if the issue is interest, we would expect to see less of a performance drop than if the interest was ability [0].
Actually, if performance continues to degrade, that would likely just be a sign that whatever negative effect is being observed takes more than ~3 months to fully materialize.
[0] Although, even thinking about this for a moment, I can envision a bunch of situations where this would invert.