That is true, but sometimes you just want an alternative route, maybe because the original route is blocked.
You can use the road block feature, but often it is easier to just drive in the direction you want, and hope that routing will soon find an appropriate alternative .
There are reports that rerouting needs many attempts until an alternative route is found.
e.g. this from @Tom
I would say that a detour of 5min / 5km is acceptable.
What do others think?