The thing is we don't know if that's the reason why the mangaka described Kamio Yui as "Supernatural Action"
It could be a coincidence that description fit the manga now.
It could be Viz just doesn't want to promote the romance aspect. It isn't so weird they want present Kamio Yui as mainly action, because they think it would be more attractive for the audience.
Why would they have an issue promoting a Romance series? They’ve promoted Romance series previously, continue to promote romance series, and have plenty of action series to promote if they want to promote an action series.
If they knew that the series wasn’t an action series and was purely a romance, or more romance than action, than promoting it as anything else is a horrible business tactic that do more harm than good in the long run.
False advertising and promoting a romance manga as an action manga is more likely to alienate their audiences than simply just promoting towards the many reader who actually enjoy and buy their romance licenses.
It’s a much more likely and reasonable scenario to assume that maybe the mangaka simply just intended it to be a supernatural action series from day one, and there is no major shift because of negative reception. It was described as a Supernatural Action from the magazine, likely described to them from the mangaka and his editor themselves, and clearly had supernatural and action elements in chapter 1. And what do you know? it went full on supernatural action