Fix s3 prefix path truncations

[tinvaan]

Closes #253

Checklist

• References any related issue by including "Closes #" or "Closes ".
  • If no issue exists and your change is not a small fix, please create an issue first.
• Includes tests or only affects documentation.
• Passes pre-commit checks.
  • Run pre-commit install && pre-commit run --all locally for formatting and linting.
• Includes screenshots of documentation updates.
  • Run mkdocs serve view documentation locally.
• Summarizes PR's changes in CHANGELOG.md

[zanieb]

Thanks for contributing!

[tinvaan]

@madkinsz / @desertaxle can one of you review/approve? I've addressed the review comments.

[desertaxle]

Thanks for the contribution!