Nothing in that implies the Dark Angels consider themselves inferior to the Ultramarines. They are different Chapters with different focus points.
Dark Angels too strive for excellence in battle, and Balthasar is just an exemplar at that even among his own. It isn't related to Ultramarines doing it better, but Balthasar being great in his own right.
Ultramarines have a bit of a stick up their backside in a lot of Chapters' eyes, and there are various traits, including logistical and tactical thinking patterns, that Balthasar might show for himself, that would result in brothers telling him he is kind of UM. Ultramarines are meticulous in battle. They're more clinical than passionate about it, and it contrasts with the Dark Angels who can often show a degree of zeal that the Ultramarines lack.
It all just points out to me that Balthasar has a more analytical and clear-cut approach to his duties than many other Dark Angels, and that he strives for excellence in what he does.