User blog comment:B214/General Discussion/@comment-90.202.240.151-20161006174801/@comment-9595671-20161007011348

...Except that there's proof it's canon. In the EX story it was mentioned that eventually a Seven Satan system was started up and something happened to Sirzechs. Volume 21 revealed the reasons for both of them.

It was based off the ending of Naruto when we met Boruto and the others, so I think that gave some basis for it being canon but still mostly minor to the plot overall.