Fix mismatch between FEASGM-style normalization and SGM-based privacy accounting

[albonec]

Types of changes

• [ x] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Docs change / refactoring / dependency upgrade

Motivation and Context / Related issue

x

mismatch between FEASGM-style normalization and SGM-based privacy accounting

How Has This Been Tested (if it applies)

Checklist

• [ x] The documentation is up-to-date with the changes I made.
• [ x] I have read the CONTRIBUTING document and completed the CLA (see CONTRIBUTING).
• [ x] All tests passed, and additional code has been covered with new tests.

Fixes #819

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D111738649. (Because this pull request was imported automatically, there will not be any future comments.)