Unity makes sense. It will give them the most relevant experience going forward and give them modern, efficient tools even if Unity's visuals aren't the best.
At least the Dragon Quest one specifically calls out "consumer game," which is what they call proper package release video games, so it won't be some mobile bullshit.
In fact, my first instinct (and this is entirely a wild guess, I don't know what this is) is that it could be some sort of DQ theme minecraft/terraria project. We've already seen a number of those pop up recently in Japan (two from Q Games alone!).