I listened to all these sorts of reassuring things when my son was a late talker and really regret it now. Has somebody mentioned Einstein yet - he probably wasn't actually a late talker at all according to biographers.
As a weary ENT specialist told me, the very first thing to suspect with a speaking problem is a hearing problem. My son fooled doctors - the GP being particularly clueless - nursery teachers, a speech therapist and us. The consensus seems to be that he taught himself to lipread and was very good at picking up on non-verbal cues. It turned out he had glue ear and was largely deaf as a result. The ENT specialist said that GPs did all right identifying a raging infection but were very poor at spotting the much more subtle signs of glue ear - a slightly pink, slight convex ear drum. I suppose I thought, wrongly, that it was a disease of over-crowding and poor conditions. He had a hearing test and failed completely. We were lucky enough to have private healthcare and a cancellation on a surgical list and within a little over a week of the test he was in hospital for grommets.
The ENT said while we waited for grommets to get down to him, face him, and speak really clearly. My son loved chocolate and didn't get it often. Standing behind him, I asked whether he wanted a chocolate bar. There was absolutely no response because he simply couldn't hear it and with me out of his vision he couldn't lipread. I was stunned. Hearing may wax and wane with glue ear - sometimes they will hear better than others. They may hear well enough to respond but not well enough to imitate the proper sound of words. No obviously I don't know whether your son has a hearing problem but people said exactly the same sorts of things to me that they are saying here. My son was older - about 3 - and it meant that certain sounds he should have learnt to say at a certain age were never learnt. He had to have speech therapy. I think it also affected his education as well because he just had gaps in his knowledge.
In retrospect, my husband realised his younger brother probably had glue ear. He too had a lot of speech therapy.
By the way, my sons could sprint at 10-11 months but neither of them turned out to be great athletes. I don't think speed of acquisition of skills affects how good you are at them as adult.