I'm not sure if I should be proud of this or not, but once I had some pretty critical field values in a Excel spreadsheet that I had to make sure were compatible with my code. I ended up adding some derived formulas in a new locked sheet within the file, committed the XLSX to Git and then created a JUnit test to make sure everything was in sync. In a nutshell, the XLSX became the source of truth

Yup, and this is frequently a total disaster. Like, hundreds of thousands of dollars get lost either in spreadsheet errors or by paying the salaries of people who manage spreadsheets when their jobs could probably be replaced by a much better solution.

But, whatever - more work for everyone! Certainly suits me. It's like wanting the average person to keep programming C because you're in infosec.

Indeed, and I think this is the real problem with non-programmer/data people working with spreadsheets. The problem isn't the spreadsheet interface itself. The problem is that people are doing what amounts to engineering without any training in engineering and no sense of best practices.