Steve Jobs said something like Dropbox was a feature, not a product. I think Bezos feels the same about literally everything. AFAIK Azure/Google have actual partnerships with the Elastic stack, partnerships that assumedly benefit both sides and have staying power.

Part of me wonders if AWS always had planned to do this, and they were just waiting until it made business sense to fork (ie they had features and a new direction in mind but neglected to implement them because Elasticsearch was good enough as is). The alternative part is just 2 big corporations not finding a way to get along. Which means without clear direction and careful stewardship I'd expect the forks to just be cleanroom reimplementations or something like that.