Probably applies to "depends". Fedora has standard installation but people's systems aren't really standard at all. So If you set up this and that you could be fine but if you set up this that and that other thing you could be screwed. I mean 10 people can preupgrade with no problem but an 11th person could have a setup that messes things up.
Does this help ya understand the issues? In other words everyone tries their hardest but the complexity of the system can't make any guarantees.