It is a genuine question. The answer lies in a close study of the facts.
The one and only time that Sri Aurobindo ever spoke or wrote publicly (addressing to the general public) about his inner experiences is the Uttarpara speech. The context of the speech was that soon after his release from the Alipore Jail he was invited by the Society for the Protection of Hindu Religion. Being full of the experience of Sri Krishna and his message about the Sanatan Dharma and by then used to speak not in any prepared way he spoke on the strength of his own experience. He did not quote any scripture but appealed to the innate psychic sensibility of the Indians of that time about the Sanatan Dharma. His experiences were incidental. The focus was Sanatan Dharma and the Indian Nation. The experience was brought in more as a scientist who had discovered something original. The tone throughout is about the glory of Sri Krishna Vasudeva rather than himself.
Yet this was a single speech where he mentions about himself. Throughout the Arya writings meant for public there is no mention of any of his experiences. But in few private conversations during the Evening Talks he shared some of these (very few) in response to pointed questions.
Later he did mention some of his experiences in response to certain questions from disciples. He also corrected some misconceptions about his life when people tried to write his autobiographical notes. But his most profound experiences and realisations were never made public. He noted them in a separate diary as Records of Yoga which were discovered in his room much later. Or else he poured them through his poems and Savitri.
As to being an Avatar he never directly spoke about it. He only indirectly referred to it very occasionally to some very select disciples (Nagin Doshi, Champaklal ji, Nirodbaran and Dilip Kumar Roy to be specific) in the course of certain conversations. It is only the Mother who made the most definitive revelation about Sri Aurobindo.
Now of course we have these quotes and compilations without the context and hence the impression.
Hope that puts it in perspective.
