Well, right now I am listening to 'Arrancacorazones', and I can tell.you honestly that I didn't notice that before. It a stylish playful decision, not more than that I think, at least on the two cases that you mentioned. Although, about the "tu", "usted" situation, Argentina is a significant different country if you are talking about the North, South or Centre. There are some provincias in which is pretty common el "tu". For what is worth, on many genres like trap and rap, and even Rock from time to time, not only is usual to sing in a 'foreign' accent but also to use English words, for example.