Summary

• document that pandas DataFrames with equal data, columns, and index can still have different internal representations
• explain that different joblib.hash values intentionally cause a conservative cache miss
• avoid attributing the behavior to a pandas implementation detail that is not stable across versions

Validation

• reproduced against the current checkout: DataFrame.equals is true while the two joblib.hash values differ
• python -m pytest -q doc/user_guide/memory.rst — 1 passed
• git diff --check

The full Sphinx build was not run locally because the optional documentation dependency set is not installed; the repository's focused doctest for the edited page passed.

Closes #1611

AI assistance disclosure

This documentation change was prepared with AI assistance. The issue discussion, current hashing implementation, all 67 open pull requests, repository policies, diff, reproduction, and validation results were reviewed before submission.