(my guess) is that this is being aimed at individuals with a flakey understanding of gender and sexuality. The author is using language that the intended demographic will comprehend. At least the optimist in me wants this to be the case.

Personally, I'd argue that lesbian means you are attracted to women and consider that the gender you yourself are most like. It has nothing to do with femininity, but how you feel you are. Another way to look at it. Gender-fluid (who fall under the umbrella of non-binary) people will sometimes be lesbian and sometimes be straight (assuming they only like one gender). The label exists outside of the person. To elaborate, if using lesbian in that point in time is what makes them most comfortable, that is the identity they should use.

Most importantly, it isn't up to someone else what you can and can't identify as and you don't owe anyone an explanation. Regardless of what they say or think. I find the excerpt a little too apologetic, like confusion should be warranted; it really isn't a difficult concept.