He does sound pretty normal to me too, although my only personal experience of GSDs is my 7 month old GSD x. However, you (and I and all big dog breed owners) need to be that bit more careful about our dogs playing with others. I've lost track of how many times my other dog has been bitten by little terrier types and it's
always laughed off by the owner. It's gotten to the point that he won't go anywhere near anything smaller than him (he's a shar pei, so not huge). However, god forbid he growl at any of these things biting him when he was totally minding his own business. He's obviously an agressive dog etc etc
I was out last week when 2 such terriers came around the corner of the woods. I remembered them as biting Dylan a while back so I called my GSD pup close to me to keep her out of harms way while Dylan skirted round them as far away as possible. He called out to me 'Is your dog friendly?' (pointing to Trin) and I thought he was just being nice so I called out in a happy voice 'yeah, she's just a puppy'. To which he replied to me 'I don't care if she's a puppy, dogs like that shouldn't be allowed off lead. They're agressive and cause a nuisance.' I was absolutely gobsmacked! My dog was under full control off her lead walking to heel, while his two rat bags were choking themselves trying to get to my pup no doubt to bite her as they did Dylan. :rolleyes:
Anyway, the moral of the story is that the big dog will always be blamed, even though (in my personal experience) it's the little ones that often start it. And playfighting in similar sized dogs often looks a lot worse than it really is. I've had complete strangers ask me whether it's really safe to keep my two together when they see them 'killing each other'. Of course no harm is ever done, but if they played like that with strange dogs (which luckily they don't!) I'd no doubt be reprimanded for having aggressive dogs!!
All I can say is work even more on his recall, and then allow him to play if the other owner is happy. But make sure you're able to recall him in mid-play in case it gets too much for the other owner to bear!! Good Luck
:-)