TL;DR: consistency > freedom

The 5th better have some good explanation on how it came to be then :/ I am all for freedom of choice but you have to admit that there are a few problems with it. If they're a splinter group that originated form Sol, it would invalidate Duck's entire history, something he put some work into for a change. Given these are early space nations, It doesn't make sense for it to be done in secret - somebody would definitely miss even a single FTL capable ship. ANd I'd rather not see many more interdimensional and any time travelers.