Cross namespaces IngressRoutes and Services

Yea, I see the issue here. Previously, one could assume that a different namespace would be disallowed.

That's right. And in some setups when you must use a single ip / port pair for your traefik instance, two sets are not possible either. On bare-metal, if your trafik listens on ip port 443 for incoming connections you cannot stick a second instance there easily to listen on the same ip/port if you do not have a second ip easily available. You will have to put those two instances behind a proxy, (perhaps another traefik) which complicates the setup even further. In other words it can be problematic.