I guess she wants to make her prospective dates jealous? Bizarre.
I feel it's a more element of the marketing toolkit: 4 out of 5 tall handsome guys agree -- I'm datable!
I think marketing is in play. She may also be doing a clever weed-out: "if you're not cool with my past / other guys, you probably won't be cool with me." And yet...it does seem a bit misplaced in the normal sequence of events...