I don’t think all of these poison/bathroom kills should be viewed as a problem with the mission design; they should be viewed as yet another indictment of being allowed to restart.
It seems as though the target only drinks from the glass once; therefore, if we weren’t able to restart, many players would have had to re-evaluate their strategy and find another way to kill him. The problem here is that players could restart and quickly rush to his glass to poison it, exploiting “time travel”, which shouldn’t be a part of the game. lol
As far as I’m aware, this is Hitman – not Back to the Future, or Dishonored 2.
P.S. If we have infinite restarts, the ICA may as well provide 47 with one of these nifty devices, too.