Sorry, this issue has arisen through my own sloppy review. Let's be consistent with the Title Case.

In the Towncrier configuration we have "Breaking Changes", "Trivial/Internal Changes", so we should have "Improved Documentation", "Bug Fixes".

Situation

[tool.towncrier.fragment.bugfix]
name = "Bug fixes"

[tool.towncrier.fragment.doc]
name = "Improved documentation"

Expected Behavior

[tool.towncrier.fragment.bugfix]
name = "Bug Fixes"

[tool.towncrier.fragment.doc]
name = "Improved Documentation"