The best you can say here is that it’s within the margin of error, in which case the effect is so small it’s literally unmeasurable. In that case the null hypothesis still wins, and you should not switch.
> Is there any reason to assume that this problem is permanent and unfixable?
IE11 as tested in the article is not getting anything other than security patches. The users who use IE11 are probably also the users most affected by poor performance since they most likely have the oldest hardware.