I'm sure it has been mentioned already, but I will throw my two cents in anyway. We were there from 3/3 - 3/11. On 3/6 there was no mention of any new Fastpass guidelines, and we used several Fastpasses late. On 3/7 we arrived at the park, and there was a reminder about Fastpass printed on the Times Guide when you entered the park, placards above all Fastpass machines and a reminder on the Fastpass itself.
I asked one of the managers that was by Star Tours responding a complaint of a guest why they made the decision to change. She told us that they were trying to keep a commitment to guests that Fastpass wait times be no longer than 10 minutes, and that by allowing late Fastpass returns, often times the Fastpass line can be as long as the Standby line.
Now, I have not personally ever found that to be the case, but we usually travel during less busy times of the year.
On the 2nd day of Fastpass reinforcement, we ended up with a Fastpass for Tower of Terror that conflicted with a reservation we had. I knew we would be about 10 minutes late. I figured if they said no, then no big deal. We were allowed on to the ride, but given a reminder that we needed to adhere to the window on our ticket. The CM said they were able to give 15 minutes of leeway.