This is part of what they mean by girl names driving the shift. You have a traditional ethnic name that may be masculine or feminine and has a baseline low level of popularity. Then you have a popular female name that rapidly gains and loses its popularity. The effect on the mix is that it's shifting from masculine to feminine, but really you should look at it as a newly-popular female name being layered on top of the traditional name. And you can often see this in the timescale, with a clear pop-culture trigger leading to the rising girl name.

Looking at just part of the data, I can see this with Arya (Stark, Game of Thrones), Paris (Hilton), Stevie (Nicks, of Fleetwood Mac), Dakota (Fanning), and Tatum (O'neal), and the masculine trend also relates to the fading of generationally-popular names like Jean (Silent/Boomer), Pat (Boomer), Joan (Silent/Boomer), Courtney (Gen-X/Xennial), etc.