I don't slow down. I think that one of the huge benefits, specially from that drill, is that your trigger control increases. I totally agree with your last sentence. Recognizing the sight picture before pulling the trigger is important, but I think that the drill shines because it lets you run a whole series of skills in one drill. I guess you might not gain the exact amount of speed as you do while dry firing but you get fluidity.
The question is do you slow down your splits to a more realistic level when dry firing?
No, I go as fast as I can.
Or is the fact the trigger finger is moving fast a good exercise as long as you see what you need to see with the sights?
I think you get the benefit of learning to shoot unconsciously from that drill.