is there a hidden requirement for legendary lost sec?

[hasty urchin]

is there any unstated requirements in legendary lost sector for dropping exotic gears?
i know i need to clear all champs for platinum clear but do i need to do it under 5min for unacquired pieces to drop?

am farming for Loreley today, yet i havent drop a single helmet stated on light.gg but a few purple helmets

thanks for ur info, i must be hella unlucky with tht 25%

[fallen wigeon]

Killing all champions before looting the chest gives maximum chance at the exotic