I can't research it at the moment, but I want to say that was a common thing in the pre-NES days, and I think Nintendo required actual gameplay graphics to be shown on the box because of that.
Could be off on the specifics, but I do vaguely recall those kinds of non-representative box art having some controversy.
Nintendo of America often used pixel art for their own box art early on in the NES era. It was similar to the in game graphics, but usually more detailed. See Metroid’s original artwork. If there was a requirement for third parties, perhaps it could be met by simply including screenshots on the back.