Why is it weird? The weird part would be letting everybody level from 1 apart from one class that gets bags, mounts, 55 levels and first aid by the click of a button.
Leveling anything to 55, then creating a DK, puts you on about the same premiss as everybody else.
yeah i think blizzard tough this one though, being able to start a dk without the lvl 55 char requirement on a fresh realm would affect a “fresh start” and “balance” the character creations allot(so they are not that stupid). on “non” fresh realms it has less of an impact not to mention that most people will buy the expansion with boost so this is good for the goldfarmers and that will benefit blizzard it seems so all good.
I think it was explained very well, you need to make a level 1 char on the fresh realm. Once you level that char to 55, you can then make your death knight, which will also be level 55.