THIS, is very very interesting.
If true, this could dramatically change the outlook on FP+.
As right now many people are counting on being able to go on at day 60 and scoop up what they want, if other people have had a 10 day head start, hrm ....
I mean, I would think you would still be able to get your FPs but perhaps not the ones you want at the times you want for the first half of your trip, depending on length. If you trip is short, well, you might actually be out of luck in that case.
I think what the poster you're responding to is describing what everyone has seen.
In other words, it's like the ADR system (180+10)...except instead of giving you a set duration, in most cases the +x is the duration of your linked tickets.
At 60 days from arrival, you can make FP+s for as long as the duration of your attached tickets are for. If you have AP's, it seems like it's essentially "forever" from that point..but only up to 10 days in advance (ie: 60 days from that date, plus ten more days after).
That's how it worked for me about 30 days ago when I made our FP+ selections. 4 of us had 5 day base tickets, and one of us had a 6 day base ticket (all via UCT). We have a DVC ressie at AKV. I was able to, at the 60 day mark, make FP+ selections for 5 days for our entire party...and could have made one more for "me".
We're going to price bridge the other 4 tickets to 6 day base when we get there. Essentially, I had 60+5 (+6 in reality...I left a mid week Epcot day open...we'll take care of those after we bridge. Also, no parks on arrival and departure day).
The thing I didn't test, and would love to see someone test, is how far you can push that +x window. Since non-expiry tickets have 14 days from first use to use their days...I wonder if you could get up to +14 (booking your first FP+ on day after arrival, and then booking another day 14 days after your first FP+), so long as you don't book more than your tickets allotment of days. Does that make sense? Anyone try it?