What kind of vendor lock-in do you even talk about. Their API is public knowledge, AWS publishes the spec, there are multiple open source reference client implementations available on GitHub, there are multiple alternatives supporting the protocol, you can find writings from AWS people as high in hierarchy as Werner Vogels about internals. Maybe you could say that some s3 features with no alternative implementation in alternative products are a lock-in. I would consider it a „competitive advantage”. YMMV.