Thats bonkers, so now not a single game can use the word, i would understand if they used "shin megami tensei" on the title too, "persona" is just a sub line of that series, like "digital devil saga" or "nocturne"
When a game becomes a hit and its referred to a single name such as "persona" and the legal lay man only calls it that then it can become a protected property in only a certain field. You could still use the word "persona" in a games name but it must different itself completely from the main seires thats know by that name. This game saddly wouldnt most likely meet that burden. A good point to emphasize this point is even though the official name of persona 2 is "Shin Magame Tensi Persona 2 Innocent Sin" you would only reffer to it as "Persona 2" or "Persona Innocent Sin" in a legal sense all 3 names can be claimed one easily due to being the official name and the other two because of the image you think of leads directly to the first.