The issue isn't Firefox getting killed as that would likely result in Firefox closing completely. I mentioned the Dock getting killed in comment 1. Moving to a macOS related component although if in appropriate here, most likely it'll end up in Toolkit::General matching original bug 1709598.
Bug 1716018 Comment 4 Edit History
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The issue isn't Firefox getting killed as that would likely result in Firefox closing completely. I mentioned the Dock getting killed in comment 1. Moving to a macOS related component although if inappropriate here, most likely it'll end up in Toolkit::General matching original bug 1709598.