Explanation
When converting a Windows-Legacy project to Windows, the project dependencies are automatically updated to the highest available version that is compatible with the Windows target framework. This is done to ensure that the project can use the latest features and improvements of the activities packages, as well as to avoid potential issues or conflicts with the legacy versions. The updated dependencies are reflected in the project.json file and the Manage Packages window of the project. The developer can also manually update the dependencies to a specific version if needed.
References:
Deprecation of the Windows-Legacy Compatibility - UiPath Studio
Convert Windows Project to Windows-Legacy - UiPath Community Forum