Is S3 built over HDFS?

I am working with flume and my sink is configured like it (and it's working).

​

agent.sinks = s3hdfs

...

agent.sinks.s3hdfs.type = hdfs

agent.sinks.s3hdfs.hdfs.path = s3a://mybucket/folder

​

So, it's correct to say that AWS S3 is built over HDFS? why we use hdfs sink (type = hdfs) in flume configuration to send data to S3?

Edit: I am using this stackoverflow question to help me with flume configuration and the answer says that S3 is built over HDFS, but I did not find any other references to this affirmation.