If I was the maintainer, I too would probably reject the PR because it didn’t remove the gender entirely.
Cool, but that isn’t what happened here. The PR was closed immediately because the maintainer considered using gender neutral pronouns “personal politics” - he had ample opportunity to clarify his stance, or simply comment ‘resubmit in passive voice’, but he didn’t. Clearly the problem wasn’t the active voice, it was the summary of the change, because when that exact same PR was re-submitted much later with a commit message of ‘Fix some minor ESL grammar issues’, it was accepted with no discussion
As an aside, I absolutely disagree with the use of passive voice. It’s more verbose, and harder for the reader to comprehend. It’s why every style guide (APA, Chicago, IEEE, etc) recommends sticking to active voice, especially in the context of ‘doing things’.
You seem content to entirely gloss over the issue, which isn’t the pros/cons of a particular writing style, it’s that the maintainer could have said ANY of the things you said, but he didn’t