No one is asking for a rule. In fact - the conventional use of masculine pronouns that you're enforcing is perhaps the closest thing to a rule that's being imposed, albeit subconsciously. Bro.
I've read enough articles where anonymous or hypothetical actors are given feminine pronouns by female authors that I'd say the convention is to favour the pronoun that represents yourself, not to default to masculine ones. Writers choice.
Huh. It's actually kind of popular in Computer Science papers in the security field to alternate (Alice, Bob, Carol, ...), and also (in general) for some male authors to always use a feminine pronoun when referring to anonymous or hypothetical actors. Surprised you haven't noticed either.