Peace Talks goes into detail that it is probably an Angel, there are limits as to how much power can be put into a swordblade , and the White Council swords probably hit that upper limit. The Swords however have far more power, and the Faithsabre more yet.
When Marcone’s Knife penetrated the Titan’s skin, it’s blade was powered by a Fallen Angel. That was confirmation of Harry, Butters and Michaels earlier speculation.
So when Butters accidentally put the Faithsabre through the wash, it probably made the empowering angel happy, as cleanliness is next to godliness.
