I am not familiar with TF, but the reason for the MTF rule is because it is very easy to delete a post. Imagine today, someone could have picked Janowicz in the first match of the day. He lost. What to do? Delete the post and pick Ferrer instead, who at that time hadn't started yet. You see the problem? No organizer has opportunity to do constant monitoring of picks. The solid deadline makes supervision much easier. And while I don't think anyone would cheat to win I'm happy that noone can be accused of doing so.
I thought a deleted post was shown as a deleted post. You can only edit or delete a post within a short time after posting it, otherwise the change is time-stamped.
It's more to help managers manage the game more efficiently. Nightmare to have to work out when each match starts and then see if anyone made a late pick. One deadline makes it much easier for managers and players to monitor the picks.
But yes it must be confusing for players of both tf and mtf.