This user's discovery is not a glitch. It is a feature of how Excel writes data to disk, and it reveals a truth about file integrity that most people misunderstand. The binary differences they observed are almost certainly caused by "slack space" or padding, Excel writes data in blocks, and the unused portion of the final block may contain old or random bytes that have nothing to do with the actual workbook. Backup tools copy the entire block, including that padding, so the binary fingerprint changes even though every meaningful cell, formula, and macro is preserved intact. The user's real-world test, restoring those backups and opening them successfully, is the only validation that matters.
For anyone managing spreadsheets daily, this has a practical consequence: stop obsessing over checksums and start trusting your restore process. If you have ever run a binary comparison and panicked, you now know that a difference is normal. The file "ends" before the allocated space does, as the user noted. This is not a sign of corruption or a failing hard drive. It is simply Excel's way of handling memory. The user tested their disk for errors and found none, which confirms the pattern. The real risk is not the backup being different, it is never testing whether the backup actually opens and calculates correctly.
The lesson here is straightforward. Verification should focus on function, not form. A backup that loads, displays your data, and recalculates your formulas is a successful backup, regardless of what a hex editor says. If you want to confirm integrity, open the file and spot-check a few critical cells. That takes seconds and tells you more than a binary comparison ever could. The user's method, repeated testing across multiple programs, is exactly the right approach. It proves the tool is reliable even when the raw bytes do not match.
Stop chasing perfect copies. Chase working copies. That is the difference between data management that looks thorough and data management that actually protects your work.