The Introduction in the Oxford edition as well as the short bio I read on Galsworthy both mention that Galsworthy was writing about his own class. He was an insider but mocking them as if an outsider at the same time.

For his time, Galsworthy was a rebel. He was a solicitor by training but he didn't like it. It wasn't until his father died that he began his career as a writer, encouraged by his wife (with whom he had a 10 year affair before they could marry). Ada encouraged him to write because it would expand their social horizons. It occurs to me now -- perhaps she was the social climber. I didn't read much about her.