How is that relevant here? You mean that when I connect to A there will be some intermediate points, that is true but those points are not setup there to track me, some points will differ, there are protocols to work around tracking at that level(using proxies and VPNs). But if I don't block the tracking scripts and cookies and I have 2 tabs with 2 different sites and both have FB code in it, FB will know I am the same person, they will search in the shadow profiles, find me, add this extra data to the profile. Then 24 more trackers will do the same,