Allegedly, on or about 15 November 2016, Gary Stainburn sent:
As someone who has a F21 server that I was just thinking of fedup'ing, what would be my best choice? (I really don't want to do a clean install)
I really just cannot imagine going through several updates-over-the-top, to get from a quite out-of-date to a current release, is going to be easier than a fresh install then customise it.
The updates are a nuisance, even if they go through without new bugs for you to deal with (some completely new, others related to incompatibility with what's left behind from previous installs). Time-consuming, storage-space-consuming, etc. And to have to do that several times over. Once is annoying enough (I stopped trying to do that years ago).
Not to mention that there's a very good chance that as you go through different releases, you'll strike things that cause new problems, with each release. Dropped and changed packages, may remove things you wanted, or make them incompatible with past data.