I recently traveled on the Getaway booking a Solo Balcony (BT). In booking, it came up as a guarantee balcony, not one of the few assigned as solo. A few weeks before departure, I was assigned a connecting room balcony on Deck 13, not one of the so-called designated solos. It was a normal balcony.
The single supplement was lower than booking a regular balcony, and I had access to the solo lounge (all solo fares now have access). However, my card was not properly programmed for this and I had to get a new card from guest services (after they told me I wasn't booked on a solo fare, sure). The solo lounge was no big deal. Usually empty, free pound cake during the day.