I imagine they probably don't do that often in filler though because it's probably easy to accidentally contradict future backstory reveals tho. Especially if a series is still ongoing when the anime is being made.
That said, I do like the filler that does build off of existing stuff instead of just pure filler.
Doesn't get to play a lot of villains like this, but he also did a great villain voice for Fairy Tail. And a great voice for the antagonist/wild card Silver Mask in Arslan.
Pretty sure with those two dead no one even was aware this happened to cover it up, since four of the five people there are dead, except maybe eventually Jiraiya when Nagato must have told him his history.