insanity, are you sure he's not part mountain goat? 
My aunt's Parson's JRT is exactly the same, never on the floor when there's an alternative surface available.
Are you going to have a go at agility with him when he's older? He'd be an absolute star at mini agility with all that bounce and get-up-and-go. Now you know why I have Lurchers. My two couldn't even be bothered to run on our walk today, just mooched and pottered with the odd trot thrown in. they are still tired from yesterday's walks and it was a bit humid, but fundamentally they're lazy! 
Pip has a real obsession with the pigeons, crows and seagulls we get in our local park. They really tease him, landing a couple of feet away, then taking off as he approaches and landing a bit further on, all the way around the park. He used to just chase them full pelt, but I was terrified he'd end up going straight across the main road, as he'd watch them in the sky rather than where he was going, so I really pushed his recall training around them and now he comes back before he even starts to run, but will come back mid-flight so-to-speak if he does decide to take off. He looks so forlorn when he can't get to them though, stands and watches them for ages.
Today squirrel tracking was the order of the day. Round and round ... and round ... and round the oak trees, following their noses all the way and not a squirrel in sight poor dogs. 
Have a bit of a problem with Lurcherboy today. On the way home from our walk he trod on a cat-food tin lid that the bin men had dropped, it clattered and clanged and he totally freaked out and dragged me into a nearby drive. I couldn't get him to walk back past the spot, he was really terrified, shaking, cowering etc. Picked up the tin lid walked away a little, showed it to him and dropped it a couple of times, while feeding hi treats, so he could connect where the noise came from and understand it wasn't anything bad and he was fine with that, but still wouldn't go back across the bit of pavement where it happened. He's made a really strong negative connection with the place, as he had no idea what happened, just that it really scared him. Tried a bit later and he'll walk towards the park there, but totally loses it and panics if I try to walk him back (which is what we were doing when he was frightened).
So, I have some work to do to get him to relax around there again, bit of a pain, as it's a few houses up from us, outside the house next to the park entrance and it means going the long-way round and a lot more road-work to use the other entrance until I've got him over it. I know from experience with another of my dogs that developed a sudden fear of a place due to illness/injury and pain association, that sometimes they just can't move on from this sort of thing.
It's amazing isn't it? One single, seemingly innocuous event and they make a strong, paired response for life, but when we want them to pair two things in training etc it takes hours, weeks, months of repetition. 