Really strange decision by KT, I can't understand it if not for the reason they gave. It will cost very little to localise a game like this that appears to be seriously shallow in content, text and voice acting. Not only that, but they're already localising all the text to English for the Asian release anyway. After that, a digital release for the West is not a huge extra investment - it's a really small one.
On top of that, there's tons of anticipation for this game online, both here and on other forums. People seem really happy about how it's turning out. DoA5 was really well received in the West, and they made tons and tons of money selling DLC bikinis. That model will, no doubt, be used in this game as well, and there's no reason to suggest it wouldn't be as successful, if not more so (seeing as this game will be lewder, there's more reason to buy the swimsuits).
So this doesn't make sense to me as a business decision at all. It's not some 'niche, barely break-even RPG' that needs extensive localisation. That's not what this is.
So why, then? It's perfectly possible that KT don't fully understand the debates the west has been having about objectification in games over the past year, and are afraid of ruining the reputation of their studio by making a game that is more sexualised than any of the games they will have seen receiving criticising online. And perhaps having that stigma follow them to DoA series proper or to Ninja Gaiden, or to lose their 3rd party contracts with Nintendo (they did Other M and Hyrule Warriors).
It's also possible that they're planning some really risque costumes for Marie Rose, and have been legally advised that they wouldn't fly in certain markets. In which case they localise the Asian version to English in the knowledge that the fans of this game would not buy a censored version. (Marie is top-2 popularity in ALL regions, according to the vote.)
But I'm inclined to believe that this is genuinely about the content rather than business. The business argument makes no sense at all.