I know that some Legendaries appear at certain places which you can reach lower than level 50, so its official that Legendaries are not based at level 50; they will be leveled according to your progress through the RP

That way, if you can get your legendary at level 25; it won't be an unfair advantage at level 50, the legendary will be level 25 as well.

Likewise if you get the legendary at level 65, the legendary wont be a lower level of 50; it will be at 65 as well.

Scaling level makes things a bunch easier and less OP and less under powered. :)