Not arguing just copy-pasting
1. We see virtually all DB characters and stories present in DBH. From DB/Z/GT/Super anime and manga, movies, specials, games only characters, and events portrayed as existing through many timelines. In fact we even already accepted things like DBO being part of Xenoverese based on this same premise alone, since it has the time breakers, time patrol and multiple story elements that cross from DBO to Xenoverse.
https://imgur.com/a/TtcRD
2. In the DBH manga it is confirmed that all DB lore is a part of the DBH world, which is considered fiction in the real world in DBH like in our own world. They literally are shown playing DBH UMX on 3DS, and said to be treated like they are watching the events just like us.
https://imgur.com/a/D9o2t
https://imgur.com/gallery/znxtw
3. We have very specific examples of many DB games and spin offs existing in the DBH world further strengthening the proof that it can all be applied to DBH.
Of course we all have seen the DB/Z/GT/Super guys present with their stories. So unless you want to see more proof on them I will not need to post scans for that.
Dragon Ball 4D with God Broly.
https://www.youtube.com/watch?v=Qhjd1i6Zuk0
Dragon Ball Minus and other stuff
https://youtu.be/vl-TA84ijHg?t=83
https://imgur.com/a/Xi3O1
Dragon Ball Z Extreme Butoden (DBHUM2 is referring to SSJ4 Broly crossing from DBH to DBZEB)
https://imgur.com/a/ZYA6x
Dragon Ball Fusions
https://imgur.com/a/PpK21
Kuriza in DBH
https://imgur.com/a/k7Lqm
Neko Majin Z
https://youtu.be/8AqumRLIUdk?t=409
Dokkan in Xenoverse in Heroes
https://imgur.com/a/iDEfv
DBS Manga and Yamcha reincarnation spin off in DBH
https://imgur.com/a/FbHyp
DB Fighter Z part of Xenoverse which is part of heroes and Dokkan
https://imgur.com/a/QXPel
Limit Break x Survivor singer (one who sings the DBS theme)
https://imgur.com/a/yoRgG
https://r3---sn-vgqsrnes.googlevide...m=34&mn=sn-vgqsrnes&ms=ltu&mt=1514333905&mv=m
Shin Budokai implied part of it (Babidi Buu is directly taken from Shin Budokai)
https://imgur.com/a/fZPzY
So, as you can see, we literally have over a dozen different DB shows, manga's, games/specials or spin offs directly being shown as part of DBH verse, and the implication that all DB lore is part of the DBH verse through the real world being just like our own, even referencing specific games and systems like DBH UMX on 3DS.
I believe this is significant proof that we can consider all the games etc as part of DBH multiverse.