Family Suites aren't necessarily excluded from FD - BUT, there is a good chance that prior bookings have been sufficient in that Disney doesn't have Family Suites to release for the promo.
Now, just as an FYI - Family Suites for week long vacations are essentially impossible to get (at least with an online availability check) prior to August 17. From that weekend onwards and through September, I can get a Family Suite to show up at rack rates in an online search.
All that means is that there are still Family Suites available - whether there are enough (or enough during the time you want to book one) to be released for FD is an entirely different matter - and something we have no way of finding out.
I think a few (but probably very few) people will get a Family Suite with
Free Dining this year - I hope to be one of them on Thursday. I'm not counting on it though.