Supposedly it's true.That's not quite true.
When B&B originally decided to have an ex-Borg on the show (stated rationale for their decision: 'Hey, why not!'), it was intended for the character to be male. It was only when Jennifer Lien chose to leave that they re-considered the role as female, to keep the gender balance of the series in place.
I thought Jennifer Lien was fired, although they did intend to fire Garret Wang, but changed their minds when he was voted one of People Magazine's most eligible bachelors, or something like that. Perhaps if Want had gotten the boot, Seven would have been a male? This is the first I ever heard that.
Voyager needed to retain an audience. Having a nobody at the time like Wang make PEOPLE means that due to his looks, people took notice. You couldn't fire somebody that had the potential to bring in an audience.
Keeping Wang & adding Seven as female is a one/two punch by having two sex symbols on a show.