I think it's a huge stereotype that feminine girls like less feminine girls, and tomboyish girls like more feminine girls but all of the bi or lesbian girls I know are like that and i'm just here like 'no one wears the trousers here we're all soft feminine whamans!' not to say that more masculine ladies can't be soft, this is a complicated topic
I think it's because the media portrays women who like women this way when in actual fact, it's not all true.
I also think that because the media portrays lesbians this way when girls have just come out, they think that dressing up a certain way will make them fit in with the stereotypical view of how a lesbian should look like or what type of woman they should be dating until they realize they can just be themselves.
There are many personality traits to someone that even if someone looks masculine, it doesn't necessarily mean they are masculine or they have a mixture of femininity and masculinity and vice versa.
At the end of the day, a woman who likes other women are just as much as a woman as a straight girl who likes guys.