It was done to my transmission by a particular shop. He said they hose it and let it sit for an hour or so to drain and evaporate. But I would still question the usefulness of it. It didn't damage the seals as far as I know and once it evaporates and the new fluid is in, should be no problem. This is a very good shop otherwise, just a strange practice, so if my son takes his truck there we will specifically request no Brake Keen.
I would change his out myself but the steel plug is badly rusted and the surrounding aluminum case is corroded. Worse, it is a big hex fitting, perhaps 3/4 or 7/8 inch. Can I try to loosen it or might I destroy it? Alternative is to pull the shift lever and change it out the top.