search history not synching properly

Hey mozilla team, I have issues with firefox sync as it doesn't sync old search history. Firefox Sync works perfectly for recent search history and chronic, but I imported an old profile (xyz.default) to firefox and logged in with my mozilla account. Started synching so that the old profile's history gets merged with the current one. It doesn't. I can see it in the imported old profile, but if I check history on another device, it's not there (aka only locally but not synced yet). Is it generally possible to add an existing profile and then syncing it to merge it with the current search history one?