it doesn't get harder from a quick water treatment.
Yes they do. I have tested this to be sure. I use straight WW's almost exclusively and air dropped they get around 12 or 14 BHN and water dropped they get to around 24 to 26 BHN and will slowly over time become softer again.
With 45's it wouldn't matter because they'll only be used at maybe 900 fps or so tops. If you want hard cast 44's you can push to 1200-1400 without leading but use them up asap because they will lose the hardness over time.