Flatten-tool has more options and functions than just that one pandas functions (But I haven't done a full comparison to all Pandas functions. I wasn't around when the tool was started so I can't say what analysis was done at the time.)

For instance I note with interest their examples on nested data and arrays. We have various different ways you can work with arrays, so you can design user-friendly spreadsheets as you want and still get JSON of the right structure out: https://flatten-tool.readthedocs.io/en/latest/examples/#one-... (Letting people work on data in user-friendly spreadsheets and converting it to JSON when they are done is one of the big use cases we have)