not exactly true.
We were in both Deluxe and non-Deluxe balcony cabins with 3 people.
One has to climb over the sofa bed when it's unfurled, but unless one is disabled, it's not horrible. Plus, the sofa was only converted into a bed later in the evening, and if you aren't ready for bed and want to use the balcony, just fold it back into a sofa. But technically, the balcony is not BLOCKED.
We folder and unfolded our own single sofa bed when we wanted to. It's not difficult, unless you are disabled.
Cabins like E522 or A512 have the upper berth in front of the balcony above the sofa, but it was super easy to just duck under it. Look for a Deluxe balcony cabin for 4 - it should have a sofa and an upper berth. The other two lower berths can be in a queen formation because they are not in the way of the sofa/upper berth.
Non-deluxe balcony cabin for 4 will have two upper berths above the separated twin beds - not a great setup for us personally, so we never booked one after watching some youtube videos. It's illustrated in post #3.