Registration of SourceTree using BitBucket Server and SSO

This was the use case provided by Robert Hobkirk from SSP-37927, I'm creating on behalf of the Robert as Robert was restricted from creating the bug ticket on JAC for SourceTree

There appears to be an issue during the SourceTree registration process whereby users can't register with SSO for Bitbucket Server..

Our users don't have access to their passwords for logging in to BitBucket and instead we need to be able to register with SSO. This appears to be missing and means that our users can't register and therefore are unable to use SourceTree.

Am I missing something, or is this functionality missing? I've reported this as a bug since it's a regression from earlier versions of SourceTree.

I've checked the Getting Started docs (https://confluence.atlassian.com/get-started-with-sourcetree/install-sourcetree-847359094.html\) but they still show the earlier version of SourceTree.

To reproduce - install SourceTree, follow the registration process and click BitBucket Server. There is no SSO option here and it requires a Username / Password.