Well the singular use of "They" is actually pretty old [1]. I don't think it is confusing readers as they did mention a name.
> I just can't help rolling my eyes at this nonsense.
I get the frustration if you are not used to the usage of the pronoun in its singular form, but it is actually sensible
[1] https://www.scu.edu/media/offices/provost/writing-center/res...
The cardinal rule of writing is Serve the Reader — Don't Make Him/Her Do Needless Work. In modern parlance, "they" is an unobjectionable shortcut when you don't know who the person is, but it's just confusing to readers when it's about a known person. I'd be fine with a coined, gender-neutral singular pronoun, analogous to how feminists coined "Ms." decades ago and it's now practically universal.
https://public.oed.com/blog/a-brief-history-of-singular-they...
What part is vague?
The cited example is just the oldest known example of singular “they”. You’ll find more examples. You’d have to rip a lot of pages out of your history books in order to come up with a timeline where singular “they” wasn’t natural English. All that is happening now is that “they” is being used more often to refer to specific, known people, which is not much of a stretch.