If you're interested in this argument, it's been going on for a little while...

Here's an archive link to the "University Librarian: It's Transphobic to Say Lesbians Are Going Extinct" article from Washington Post: https://archive.is/G6JAI

It references this great article by Katie Herzog, "Where have all the lesbians gone?". Would recommend a read if you haven't seen it before!

One ridiculous claim, out of many, from the librarian article:

The degree to which some girls embraced these empowering options, however, prompted a backlash associating tomboyism and homosexuality.

Tomboyism and female homosexuality were already associated; "gender nonconformity" is much more common among women who are lesbian (or bisexual).

Notice how she uses the phrase, "lesbian extinction rhetoric." She is trying to other any discussion of the possibility that lesbians are going "extinct."

The most reasonable counterargument she COULD make, is that homosexuality is a phenomenon that arises naturally in nature and there is no chance of it going "extinct." But to make that claim, she would have to define "lesbian" as a homosexual, i.e. exclusively same-sex attracted, woman. And she doesn't believe that; she believes that the word "lesbian" is defined on the basis of gender, not sex:

By this, she meant that identity categories like “lesbian” are useful, since they’re key to securing civil protections and other rights that are tied to minority groups. But by the same token, she argued, those categories are too static, never truly capturing or describing the many individuals who use them. After all, knowing someone’s sexual identity — lesbian, straight or otherwise — tells us very little about that person except the gender to which they’re generally attracted.

(I wonder whether she's actually lesbian if that's how she defines "lesbian," but whatever.)