lol. (Sorry - it's always a little funnier when the furniture destruction happens to someone else.
Our Cooper had a thing for furniture destruction, too. He was nearly three before he could be trusted. And even then, it was iffy.
I noticed that you said he chewed up the armchair after a vigorous play session. If it happened shortly after you came back inside, he could have still been a little "hyped up" from playing. Is it possible that he wasn't completely worn out, still had the juices flowing so to speak and needed to find an outlet? I've noticed with our Goldens over the years (and our GSDs even more so) that unless they were completely
worn out, it takes them a while to sort of wind down after vigorous play, and they're more likely to act up or be destructive until they do.
I'd still crate, though, just to play it safe.