The guy who said horses pick up on nerves is spot on. We had a mare once that couldnt be ridden by a nervous person as they freaked her out and yet she was a sensible boring ride for a confident rider and competed in dressage, showing & jumping really well. It made me realise that some horses are just more sensitive than others
My other thought is that 30 minutes of groundwork is quite a lot for a young horse to concentrate on and he might just have been saying 'stuff you I've had enough of this'
My pinto and our older Irish Draft both get a bit up themselves when they have some time off, especially when its cold so I do give them a short lunge session before I get on or I know I'll get some crow hopping and pinging around but the horse you have sounds more like he was really unhappy and fractious