There is a lot of software that directly implements the HTTP S3 API. That API is also documented by Amazon.
E.g. the last implementation I saw was by DuckDB https://github.com/duckdb/duckdb-httpfs/blob/main/src/s3fs.c...
E.g. the last implementation I saw was by DuckDB https://github.com/duckdb/duckdb-httpfs/blob/main/src/s3fs.c...
Their only real inherent commitment here is to whatever backwards-compatibility expectations are being set for their first-party SDKs. If they fulfill that but other vendors can't or won't follow suit, the outcome is gonna be different than it would be for an actual standard rather than an assumed one. There is no meaningful leverage for the third parties to exert to force a community-favored outcome if Amazon decides otherwise.