The in game description says you "Gain a +1 bonus to AC while wielding a melee weapon in each hand." It however, does not give the AC bonus. The ability to dual wield 2 non light melee weapons works fine.
Confirmed bug, have the same issue on my char after choosing this "gift" at lvl 4 : - The +1 AC bonus is not added --> NOK - The gift "Dual wielder" is not displayed anywhere on my char. page - The ability of wearing 2 non light melle weapons is OK