Unless there is a noticeable deformity or caught during a routine physical most of the time it goes unnoticed. Girls at that age are awkward anyway - some with poor posture, shy and still not used to changing body so they stay covered up - difficult for a parent to notice a deformity unless the kid is in a bathing suit. As goofy as the Browns are I wouldn’t fault them on missing this. With the kids not attending a public school until later they probably were never screened - in Texas kids are screened in 6th & 9th grade - all states have some kind of required screening in public schools.
The thing I find most irritating is the putting off of the surgery. I’m a pediatric nurse and have taken care of many kids after scoli surgery - majority of the time the prognosis is great and all the pain of surgery and the tough recovery is so worth it in the end. The surgery is no joke - very painful, the kids are in ICU for at least 24 hours then spend average of 5 days in the hospital.
The whole scar convo - geez, having a scar down the back should be the least of your worries. These people need to get their priorities straight.