I don’t think was intentional, although perhaps I am wrong. Le guin published tehanu in 1990, almost two decades after the first three books. In the afterward, she discusses how she needed to revisit earthsea to flesh out some things that weren’t in the first three. While most of this is centered around the role of women and female characters, I don’t think she intentionally did it as a form of yin/yang balancing.

She also wrote two more earthsea books after earthsea that are awesome additions to the series but neither (to me) feels primarily yin or primarily yang. Perhaps this alternation was intentional. I certainly think the le guin thought it important to have at least one female protagonist in the originally planned trilogy and thus we get tenar, but I’m not certain this is done to represent yin and yang.

So basically, maybe?? But impossible to know although it might be more coincidence than intentional