It's extremely logical for stubborn men to not see a good option in front of their eyes because of their stubbornness. Sometimes, a very small amount of very stubborn persons are also very bright, bordering genius in their field, and if you are often right, being stubborn is more of a quality than a flaw. Koeman is not one of those rare cases.
Indeed. Despite the good showings Riqui Puig had last season, Koeman basically made up his mind before he even gave him a chance in a proper match. It's a strong bias thing, doesn't think much of "fragile looking" midfielders like Riqui Puig. Not comparing their talent but bet you if it was Foden or a very young Xavi instead of Puig, they'd be on the bench as well.