Purity's Edge Greatblade rumored to only drop for level 60s?

Purity’s Edge Greatblade is a great looking two-handed Paladin sword with a Silver Hand motif. It only drops from the “Penitence of Purity” treasure in Bastion; which requires the Kyrian covenant and the Anima Conductor to be able to loot it daily. Hypothetically, it has a 4% drop rate, which isn’t so bad.

However, a lot of players are reporting that it absolutely would not drop for their level 70 characters, and only dropped when they went to loot the item on a level 60.

Quoting another player by the username of Nex1080:

Update 2 (Patch 10.1.5):
Today, after well over 1000 chests opened, I’ve finally received this sword with a level 60 Paladin at Renown 61 with Bastion on the first try.
After months of farming I grew suspicious about this sword. Does it even drop for characters that are lvl 61-70? Is it a bug perhaps?

This isn’t the only player to report this difficulty, and this is deeply concerning if true.