When I to a git-flow initialization on a new local repo I typically make two modifications to the default settings: change the Production Branch to "main" and change the Version Tag Prefix to "v".  When I do this initialization with Sourcetree and then check the .git/config file, the branch name has been changed, but the version tag is blank.

Note that in the steps to replicate below I needed to create and commit a blank file in order to create the main and develop branches — I was unable to create new branches using Sourcetree with a completely blank repository.  Once those branches exist, I could initialize git-flow.

Steps to replicate:

1. Create a new local repo
2. Create and commit a blank file
3. Create the main and develop branches
4. Select Repository–>Git flow/Hg flow–>Initialize Repository
5. Change "Production branch" to "main"
6. Change "Version tag prefix" to "v"
7. Click OK
8. Look at .git/config:

[gitflow "branch"]
 master = main
 develop = develop
[gitflow "prefix"]
 feature = feature/
 bugfix = bugfix/
 release = release/
 hotfix = hotfix/
 support = support/
 versiontag =

 The second line shows that the modification to the Production Branch worked.  The last line shows that the modification to the Version Tag Prefix did not work.