We were there the 1st-4th and there was no mention of it and we used late FP's many times.
I think if DL is ever going to enforce the FP return time, they are going to have to get their ride closure issue fixed. I can't tell you how many times we either went to get or use a FP at a ride and the ride was closed. Space, Indy, and TM seemed to be closed more than open while we were there.
To be fair though, thats not really a big problem. Usually when a ride breaks down, dont forget it affects the people ALREADY in line as well and not just FP holders. And for those people, if they are far enough in the line when it breaks down are just given a re-admission pass which basically works as a FP and that they can jump ahead of the line if its woking later when the problem is resolved. Same thing can be done for FP holders, just given another ticket to come back at any time of the night!
And usually only a fraction of the people end up coming back anyway since they get busy with other things or simply leave too soon, so it doesnt cause a huge problem with line back ups.
That said I dont think its a huge deal if they keep letting people return after their FP times. I'm pretty sure most show up in the window because remember most people WANT to ride an attraction ASAP and not hold off until later. And frankly if it was that much of an issue, Disney wouldve put the brakes on it years ago!
It looks like with just a few days to go, nothing will change anyway, but it doesnt mean it will never change, just not in the near future it looks like.