I realize that the agent reading the bio of a query wants to see relatedness between the writer and the subject about which they write, so with that in mind - can revealing help or hinder in any way what a prospective agent thinks when weighing the merits of the writer against his/her work? I know it may help if I want to write some legal thriller novels, but I am only interested in the YA and children genres.If you're writing nonfiction, then yes, we really do want some reason to think that the nonfiction is not full of mistakes copied from Wikipedia, or "facts" revealed to you on a piece of toast by Jesus.
If you're writing fiction, there doesn't need to be any related experience with your subject.
If there is-- if you're writing a legal thriller for teenagers and you have legal experience, or have actually been to juvie yourself, that's just gravy.
If there isn't, just try not to say something weird, like about your advanced degree in grandmotherhood / cookie-baking or how you're writing about teddybears because you have the ability to hear their thoughts.