Our sincere apologies, somehow we (SODA team) missed this question. Sorry for the late response!
Not sure I understand the issue though... are you saying the version has the same value for different inserted documents? If those documents have exactly the same content, then this is expected, assuming you're using SHA256 versioning method (which is the default). For this default versioning method, the version is simply a SHA256 hash of the content. So, if you have two or more documents with the same content, their versions will be the same. Versions are only there to indicate that a document content has changed: any time the document gets updated, assuming it has a different content, the SHA256 version will be different. This is useful for things like optimistic locking or for generating eTags in REST type apps. Versions are not used to compare different documents (i.e. documents with different keys).
Does this answer your question? If not, please let us know.