fix: default length units not being used properly on arc creation

[RobPasMue]

Description

Problem related to the way default units are consumed inside the arc creation based on points.

Issue linked

Closes #1304

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate unit tests.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have added the minimum version decorator to any new backend method implemented.
• I have made sure that the title of my PR follows Conventional commits style (e.g. feat: extrude circle to cylinder)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.07%. Comparing base (0535c1f) to head (18f1fe4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1310   +/-   ##
=======================================
  Coverage   92.07%   92.07%           
=======================================
  Files          85       85           
  Lines        6598     6600    +2     
=======================================
+ Hits         6075     6077    +2     
  Misses        523      523           

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