Zdravo to everyone and welcome to my page!
A few reasons why some think he may be a Serb:
1. Last name: Kovic, or Serbian - Ković; but he also may be Hungarian, as his first name, Lazlo, is Hungarian. Also, a variation of his last name, Kovacz, is also Hungarian.
2. Involvement in Bosnian Conflict - if possible, one army, who has intention to attack any country, will deploy, if possible, a number of men/women who are associated or have any kind of connection/knowledge about the people, cities, places, culture and heritage of the "attacked" country, on it's soil (intelligence purposes). That's a case with Kovic.
Something you might not know: To ones who are not familiar with Serbian names and their meanings, names like Dragan, Zoran, (a nickname) Draža and so on, could sound though, badass or ruthless to them (just as their carriers- in this case, villains from this game), but those names have, actually, an opposite meaning. For example, Dragan means "dear, darling", Zoran means "one who brings the daybreak". Draža (previous villain with "ruthless" name) is short for a various names such as Dragan, Dragoslav, Dragoljub, etc. and means "even dear(er) person".
Knowing this, you might find the irony in the opposition of their names and their personalities.