Yes it's a curious feature of JW rules that they have not outright banned JWs from marrying non-JWs.
If there were enough eligible JW brothers for all the sisters, they might try it. But with the slim pickings available at most Kingdom Halls, they would lose many sisters who, if forced to choose, would leave to wed their unbelieving beau instead of staying in the congregation as a Watchtower spinster.