No they don’t. They use their own servers, the Xbox live servers are (obviously) hosted by Microsoft, the DDOS website uses your gamertag to generate packets between Xbox live and Ubisoft servers, meaning that while connected to Xbox live you’re susceptible to DDOS and separation attacks

Going back to my Battlefield point, the reason DDOSing on BF or even COD is almost nonexistent is because the packets sent from A to B are client to client, rather than Ubisoft’s Client>host>client. Aka: you can’t DDOS a server without DDOSsing yourself.

Ubi could easily fix this (and may even fix it via the introduction of cross play) by changing how packets are sent and received from interpolation to extrapolation, or client to client.