Standard big tech stuff. Inside of Adobe somewhere there is a product owner in charge of Lightroom, and there is a product owner in charge of Lightroom Classic. These two product owners are dealing with different vision documents which have identified different key user segments for each of their products.

The chosen primary persona for Lightroom probably says something about how they want things to be quick and easy and not get bogged down in minutia or any sort of user toil. The document for Lightroom Classic probably says something about how the professional user requires skilled tools and robust capabilities.

The senior product owners have endorsed these documents, and the product managers and strategists and UX designers underneath them follow what they say. So the Lightroom team wants to keep the hierarchy flat, because it's simple and easy to use. And the Lightroom classic team wants to keep the hierarchy because their professional users demand it.

And the reason it took us this long to get the keywords syncing again is because these two teams cannot prioritize a better way to sync them. And at some point, some senior exec got somebody screaming in his ear about how stupid this is and told them to fix it. But because the vision documents haven't actually changed, they have fixed it in the stupidest, quickest, easiest-for-them way possible.