Thanks for getting back to us with that question tool, it’s appreciated.
When a phone call comes in, the blocked list is searched to see if it should be allowed. So yes, the blocked phone numbers need to be included in the Block List.
You mentioned you sync your information and data to iCloud. Do you happy to also back up your iPhone to iCloud as well? If you do, this article provides the steps to locate your iCloud backups: Locate backups of your iPhone, iPad, and iPod touch - Apple Support
If you’re able to locate an iCloud backup, see if the blocked numbers are there by restoring the backup to your device: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
We also want you to be aware that restoring any backup reverts any new data you’ve added since the date of the backup will be removed. To keep that from happening, we recommend backing up your iPhone to a computer:
How to back up your iPhone, iPad, and iPod touch with your Mac - Apple Support
How to back up your iPhone, iPad, or iPod touch with iTunes on your PC - Apple Support
Please let us know the results when you're able.
All the best.