Adding a contribution replaces some existing data, in specific case?

[JoshuaKGoldberg]

Describe the bug

I asked the bot to add me as a maintenance contributor in a repo that had been pre-populated with a table. It removed my two existing contributions -tool, design- in the process.

To Reproduce

1. See this comment: 🐛 Bug: Horizontal offset on Updated Since date input in mobile Android JoshuaKGoldberg/tidelift-me-up-site#8 (comment)
2. See this PR: docs: add joshuakgoldberg as a contributor for bug JoshuaKGoldberg/tidelift-me-up-site#13

Expected behavior
Don't delete existing contribution types? Or if they're invalid in some way (are they?), mention that somewhere?

Additional context

This might be the reproduction for all-contributors/cli#355, finally? fyi @Berkmann18

Edit: it seems to be happening reliably on that repo. JoshuaKGoldberg/tidelift-me-up-site#56 (comment) -> JoshuaKGoldberg/tidelift-me-up-site#58

Edit: and also here! JoshuaKGoldberg/refined-saved-replies#172