If you read the article though, many of the updated nodes (which are now garbage) don't see any updates to their “data” but to internal tree pointers. So lots

If you read the article though, many of the updated nodes (which are now garbage) don't see any updates to their “data” but to internal tree pointers. So lots of “data” is being copied, and garbage is being generated, only for the benefit of tidying up tree structure, not because the actual “data” in those pages changed. Not generating such garbage in the first place is an obvious benefit.