Hmm...any available award seat any day of the year might be the catch here.
That's not the same as any open seat, any day of the year.
Potentially they could still block days off -- allocating zero award seats to all flights operating on 11/25 for example. It's not blacked out, but there are no award seats allocated to any flights on those days. That would be kind of snakey if they did that, creating de facto blackout dates systemwide but not calling it that. Hopefully that's not what they are doing, and I give them the benefit of the doubt they are not doing that and publicizing it as some new benefit.
(I think there's a Simpson's reference in here somewhere. A certain percentage of seats are allocated to free travel on every rlight, every day. What's that percentage? Zero percent.)
More likely, in my opinion, is that they are no longer simply pulling certain dates from the award travel calendar. Perhaps a "standard" allocation of award seats is allocated even on the most desirable days. There may or may not be some fine-tuning to those numbers. But what this likely means is that you do have a chance at using award tickets even on the most desirable dates, possibly even in all markets or all flights. But I suspect it does not mean any seat, any flight.
One other note. It's fairly common for the PR side and the technical (pricing, website, inventory, etc) side to not be in perfect synch. It wouldn't be a surprise if PR announced this but award inventory has not been released to formerly-blacked out days or flights. Or....this may be something they rolled out days or weeks ago and waited to do PR until they were sure it was working correctly, and in the mean time people snapped up the available seats on the most desirable days not knowing they were "supposed" to be blacked out.
It might be that PR is often out of synch like this at other airlines, too. But because some of us watch this stuff like a hawk for Frontier, we're keenly aware that it does happen here and wouldn't know if (for examlpe) JetBlue has similar issues.