Removing iPhone from find my for insurance claim

Simply turning off Find My does not erase your iPhone.

Turn off Find My on your devices and items - Apple Support

However, you likely failed to include other pertinent information that would strongly suggest you should erase your iPhone. Erasing the iPhone will, of course, destroy its contents. But if those contents are housed elsewhere, that should not be an issue.

If you are making an insurance claim, that would mean that you no longer have the iPhone 6, right? That it has been lost or stolen? If you don't have physical possession of the phone, there's no way for you to remotely copy pictures and messages stored locally in device storage, on the phone itself.

You would need to try to recover your data from other places. E.g., if you were using iCloud Photos, you would be able to recover any photos that made it to iCloud, and could see them from a Web browser by logging into iCloud:

https://www.icloud.com/

If you were not using iCloud Photos, but you were backing up your iPhone and including photos in your backups, your photos might be in a backup (from where you could get them back by restoring the backup to a new phone.)