Wouldn't this partly be a sign of markets deciding what wait time is worth it? For non-emergency surgery, like cataracts or knee replaces cited in the data, people can live with the conditions. It looks like wait times are consistent, meaning the backup isn't growing steadily over time. I'm pretty sure that would mean different populations just have a different threshold for how long they're willing to wait. If it was a consistent imbalance between the number of surgeries needed and the medical capacity I would expect to see wait times grow over time.

Perhaps this is related to the fact:

Cost of medical treatment and holidays included still cheaper than America?

Fits perfectly for non-emergencies.