The CLI has long had `-noremote` for a long time to tell it you want a second Firefox. It's useful with `-ProfileManager` or `-P $profileName` for multi-profile workflows, which are out of fashion this decade, especially with Multi-Account Containers being able to do most of those workflows in the same browser window now with different tags. But some of us still have ancient profiles for ancient reasons and ingrained habits regarding them.

Ancient documentation: https://www-archive.mozilla.org/docs/command-line-args.html