Leslie is used as a boys name...
It is (always was) a boys' name - yes, there are some which end in 'ie' but quite a few of those are ones which have become 'girls'. In that case, as Lesley, but as mentioned Lindsey, Hillary and Shirley.
As the piece said, this isn't new and it's pretty much only a one way street. Growing up in the 60s and 70s, I was surprised by finding that many names of girls I knew had once been 'boys' names - Kim, Vivian (spelled that way, not the 'feminised' Vivienne), Hilary, Evelyn, Beverly. Leslie/Lesley was about the only one I can remember which was used for both at that time that I knew of.