It is implied that one with a karma seal is not a normal human. What if that is because it allows one to subvert the rules of the narutoverse and become like a god with the ability to surpass or alter space time? So in a sense it turns one from a human to a player who's focus is to level up his skill with this new ability. Momoshiki and Jigen are the veteran players who seek to update the system by passing the seal on to another. Boruto and Kawaki are like the next gen consoles with the potential to achieve higher levels. Take Kawaki for example he can absorb chakra but cant use ninjutsu. Thats completely broken and unexplainable unless you consider that he is a player and not a human. Before him you would need to achieve six paths level for such a feat. Just something to consider.