Definitely a money ploy in my opinion, just a rebranded solo-supplement. Regarding the lounge access perk booking a a non-studio solo, on my last cruise we had folks just ask the cabin stewards to let them into the lounge, even if they didn't book a studio.
Also, in this case, it actually costs a dollar more to book a solo balcony! 😄 (7-19 April 2024, TA)