If you go to the gear screen of a sader with at least 1 legendary and at least 1 non-legendary, click on a legendary, then click really fast on a non-legendary, you'll get a Disenchant button on said non-legendary. Then if you CLICK that button (it needs to be on a gear with an even number of recipes) you get a L upgrade screen for a non-legendary gear! Upgrading gives you the Disenchant message, and disenchanting won't do anything, but it's still really weird.
https://snipboard.io/cRC759.jpg
https://snipboard.io/Rbkhxg.jpg
The buff does show up properly after area 25. If you're not seeing it, reload the game.