Fastest or not? The context has the say.

Whether he is still the fastest one depends on the context:

1. He has been the fastest one in the team for two years. (possiblly ‘no longer the fastest’ is indicated if the speaker said this 3 years after the first record)

2. He has a unique athletic build. He has been the fastest one in the team since the team started. (most likely still be the one)

3.He has been the fastest one in the team until an accident from a competition. (apparent)

This grammar phenomenon agrees with what I remembered reading from text book:

现在完成时表示动作发生在过去并一直持续， 现在可能仍在继续或停止了。