Does this sound like normal language development to you?

I'm really not all that concerned with this. My son is developing at his own rate and I'm sure words and everything else will come in time, but my husband things that there is a serious problem, and even my son's doctor wanted to set up a followup appointment to check up on his communication skills. He is 12.5 months old, doesn't know any words. He jabbers a lot, and he experiments with lots of different sounds, but he doesn't really say any real words, or even sounds consistently. He doesn't show any understanding of words that I say at all, and he doesn't really understand or use the signs that we have been using since he was 7 months old. He'll wave to people if they wave at him, but he doesn't ociate waving with "bye bye" or anything like that even though we have been trying for months. I know he has good hearing because we play a whisper game where I hide and then whisper for him and he comes and finds me. He also loves music and dances to it regularly. I really doubt he is autistic or anything because he has good eye contact, and he loves to interact with people. He just doesn't communicate. Every other milestone he has met on time and most even early, so I'm really not worried at all about his development. He couldn't be ahead in everything. Every child is different and develops at a different rate... so why is his pediatrician concerned about this? he's been a great doctor so far, and I've been really pleased with him up to now. Does my son's development sound normal to you, or am I missing something?