In this article, for instance, we see the text:
the South Korean ministry noted that Fifa has already set the precedent of banning the rising sun flag at international football matches.
I've searched around and I've been unable to find anything except this article stating:
A professor [...] will begin a campaign to prevent Japan's Rising Sun flag from being used at the FIFA Women's World Cup 2019.
Although the second article is from a few months earlier, it seems odd that they'd campaign about a single event if FIFA had banned it at matches.
I've searched the FIFA web site, but all the hits are for "Land of the Rising Sun" cliches.
Note, there could be conflation by the Korean ministry by claiming the flag is a political/racist statement thus it is by definition banned under existing FIFA rules.