TEST: hollow out models on close

[braingram]

Regression tests: https://plwishmaster.stsci.edu:8081/job/RT/job/JWST-Developers-Pull-Requests/1630/

Resolves JP-nnnn
Resolves RCAL-nnnn

Closes #

This PR addresses ...

Checklist

• added entry in CHANGES.rst (either in Bug Fixes or Changes to API)
• updated relevant tests
• updated relevant documentation
• updated relevant milestone(s)
• added relevant label(s)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.23%. Comparing base (4d7c3a6) to head (cb8554e).
Report is 32 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #312      +/-   ##
==========================================
+ Coverage   64.84%   66.23%   +1.39%     
==========================================
  Files         103      101       -2     
  Lines        5694     5405     -289     
==========================================
- Hits         3692     3580     -112     
+ Misses       2002     1825     -177     

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