Shirou's persona Izanagi gives him advice that lead to him working with others. While one could say it is a form of a tutorial for him as the investigation team seems like something that simply has to be formed, what if it is instead doing the same thing that Persona of other arcana are doing? That is, helping Shirou with making one of the Fool arcana get over their problems, the person in question being Shirou himself and the problems being his inability to see himself as a human and his attempts to shoulder everything.
Yosuke's Risette facts do not help Teddie locate Rise's dungeons because not only of her identity crisis regarding Risette, but because as an Idol Singer, most of her "information" is controlled by her Production company to be more marketable, just like her actual bust size is two centimeters smaller than what is reported.
Adachi pops up a lot less around the Investigation Team than in canon. This is because Shirou's magusparanoia instilled the value of secrecy of anything supernatural into the Investigation Team lest all of them get Killed to Uphold the Masquerade, which incidentally kept Adachi from figuring out their involvement in the murder case as easily as in the series and thus he didn't see the need to mislead them with his deliberatelychattydumb copact.
Mitsuo mentions that his parents haven't been home for a long while his sister telling him they left for their second honeymoon. When it's revealed that his "sister" is actually Satsuki Yumizuka, it brings a whole level chilling as too why he hasn't seen his parents in a long while. She later confirms that she killed and ate his parents.
If Shirou isn't in Fuyuki helping Sakura Matou, then she's lost her Morality Chain. Rin's not going to care and Zouken and Shinji will be Sakura's only real company for a whole year. Considering Sakura was a Tyke Bomb in canon who knows how bad that's going to get this time...
