I mean I get what you're saying but people have differing standards of what constitutes attractive musculature especially for men and women. Or even just what works for the characters.
Take the Hulk and She-Hulk. He is
a full-on Ogre/Giant-looking fellow, while she is closer to
a beautiful fitness model (or
maybe a good-looking female bodybuilder depending on the artist). Oh sure,
some people draw musclegirls as borderline masculine in build, but
sadly some people hate the idea of girls with such explicit muscles.
Also worth bearing in mind is that Brint and Brienne have differing personalities and sexual tastes. Not in that they aren't both bisexual (or at least player-sexual to a degree) but moreso that Brint is very dominant and aggressive, and wants to top most of the time, but Brienne is more submissive and like a wifey type to us. In that sense, the whole
massive, built like an apartment block density of musculature can be said to work perfectly for Brint but for Brienne,
a slimmer and more feminine but still muscular build works better. Not that even once
she's pregnant, she's still plenty strong and capable. She just needs to adjust her stance and how she carries herself.