@suggestionsplease1
In terms of data taking time to filter through, you would surely expect the impact of policy change to be largest during the initial period after it is introduced, and then a tapering effect to occur thereafter, wouldn't you? That should be pretty visible in countries by now, but that does not seem to be the case.
First, the Finnish change is so new (four months ago) that there would be no data yet, the NZ is a couple of years so not much data. There was a suggestion by some that the Norwegian data showed an increase in rapes committed by women the year after Norway changed the law, but I haven't had time to look into this more.
But, second, all statistical data takes time to gather and to condense which means that the most recent year available for all sorts government statistics, say, is often three or four years earlier. We are still waiting for most of that data.
Third, the effects of all such changes are not necessarily of the type you describe (an instant blip and then a tapering off), because some effects take time to appear.
Take the example of something like women's weight-lifting in sports (where men have a clear biological advantage):
The impact of allowing trans girls and women to participate will not be instantly visible and it will not even be clear for some number of years. But the longer term effect could be that girls will stop being interested in that sport altogether, knowing that they will never medal on the elite level. So some changes might take a generation to become visible.
O, and plenty of people think transwomen are less likely to be as good at their jobs, in IT or otherwise.
That is a different problem from the assumptions of male biological superiority in certain fields or from the inequalities created by pregnancy. A male IT person transitioning after many years of work in the industry is not suddenly going to be suspected of having forgotten how to code or ranked as not to be promoted due to the fears that she might suddenly fall pregnant and leave. When trans women are viewed as satisfying the female diversity goals of an IT company the underlying problems are not actually addressed.