If there _were_ a substantial contingent of native English speakers who don't interpret pronouns as conveying sex category information, one would expect this to show up in our cultural corpus more often—and yet, I'm actually not aware of any notable examples of this (if you do, let me know in the comments). In contrast, it's very easy to find instances of speakers treating pronouns and sex as synonymous. As an arbitrarily chosen example, in [one episode](https://theamazingworldofgumball.fandom.com/wiki/The_Nest) of the animated series [_The Amazing World of Gumball_](https://tvtropes.org/pmwiki/pmwiki.php/WesternAnimation/TheAmazingWorldOfGumball) featuring the ravenous spawn of our protagonists' evil pet turtle, the anthropomorphic-rabbit [Bumbling Dad](https://tvtropes.org/pmwiki/pmwiki.php/Main/BumblingDad) character [says, "Who's to say this pregnant turtle is a _her_?" and everyone gives him a look](https://www.youtube.com/watch?v=5N2Msnrq7wU&t=14s).
The joke, you see, is that bunny-father is unthinkingly applying the stock question "Who's to say _X_ is a he/she?" (which makes sense when _X_ is, _e.g._, "the nurse") in a context where there's an obvious answer—namely, that the referents of "her" pronouns are female and only females get pregnant—but the character is too stupid to notice this, and we enjoy a laugh at his expense.
If there _were_ a substantial contingent of native English speakers who don't interpret pronouns as conveying sex category information, one would expect this to show up in our cultural corpus more often—and yet, I'm actually not aware of any notable examples of this (if you do, let me know in the comments). In contrast, it's very easy to find instances of speakers treating pronouns and sex as synonymous. As an arbitrarily chosen example, in [one episode](https://theamazingworldofgumball.fandom.com/wiki/The_Nest) of the animated series [_The Amazing World of Gumball_](https://tvtropes.org/pmwiki/pmwiki.php/WesternAnimation/TheAmazingWorldOfGumball) featuring the ravenous spawn of our protagonists' evil pet turtle, the anthropomorphic-rabbit [Bumbling Dad](https://tvtropes.org/pmwiki/pmwiki.php/Main/BumblingDad) character [says, "Who's to say this pregnant turtle is a _her_?" and everyone gives him a look](https://www.youtube.com/watch?v=5N2Msnrq7wU&t=14s).
The joke, you see, is that bunny-father is unthinkingly applying the stock question "Who's to say _X_ is a he/she?" (which makes sense when _X_ is, _e.g._, "the nurse") in a context where there's an obvious answer—namely, that the referents of "her" pronouns are female and only females get pregnant—but the character is too stupid to notice this, and we enjoy a laugh at his expense.