Why didn't Frieza know about Goku and Kid Buu's fight? In Dragon Ball Z, when Goku was fighting Kid Buu, there were many enemies watching him from Hell.

From DBZ Wikia article on Hell: 


  In the Kid Buu Saga, during the fight with Kid Buu, the ogres are seen watching the fight alongside Cell, Frieza, King Cold, Recoome, Burter, Jeice, Guldo, Dr. Gero, Appule, and Babidi.


However, when Frieza was revived, he didn't know about the fight with Majin Buu.

Is there any reason as to why this is so?
As stated in the Wikia article on Hell (emphasis mine):


  Hell (Jigoku), or HFIL (Home For Infinite Losers in the edited English dub), is a place in Other World where evil characters (and sometimes, in the case of Piccolo, Goku, and Pikkon, protagonists) go after they die. Hell is never actually shown in the original manga, but it is shown several times throughout various medias of Dragon Ball.


Hence, it's an anime inconsistency which is not the fault of Akira Toriyama. One can only assume that the scene was not taken into account in Dragon Ball Super because they adapted it from the manga and didn't take into account the anime-added filler.