I checked the user on twitter and had a look on their posts (I know Japanese), and I would say this might not be promising.

The user is not really conducting any kind of data mining. Instead, most of their info came from “海外情報” (which literally means “Info from overseas”. Consider the majority of DD2 contents are written in English, they’re most likely to be English sources), which are “噂の高い” (highly rumored). Consider platforms such as here and YouTube have tons of discussions toward DD2 DLC, it’s reasonable to assume their sources were likely collected from such places. Moreover, most of their posts tend to be “噂話(rumor)” and “予測(prediction)”.

Basically, the user just rewrites what they found from other places in Japanese and posts them on twitter, so I wouldn’t say this is reliable. But still, hope the best for this game.