In which cases do you want to discard an action card you show from your deck with Scrying Pool?
Here are 3 (2 really obscure) cases off the top of my head:
1. Possession probably does some wierd things (I am possessing my opponent and accidentaly played a Possession (through Golem), so now I want to screw my own deck with Scrying Pool, because he will play with it the next turn. (or maybe I just want to have good actions on the top of my deck anyway, cause I don't have Scrying Pool in my next hand)
2. I have also Golem in hand, but there are not-optional trashers in my deck (Remake) and I want to play the Golem, but want to have a better chance that it does not show the Remake. Also I have to reshuffle for this to make a difference. (is there ANY chance this is gonna happen?)
3. My deck is not good enough to reliably draw itself every turn, so I want to discard some Scrying Pools/drawing cards and reshuffle so I have them in my next hand, because they will be useless in this turn anyway. (this is probably the only "happens occasionally" situation for this "exception to the rule")