Form 1116 is only needed when a single filer has $300 or more in foreign tax paid.  Married filing jointly = $600 or more.  That would be why Form 1116 wasn't used during 2019.  As far as the credit being limited. could be based on their overall tax liability.  Meaning if they don't even have $99 of tax liability, then they wouldn't use the whole $99 foreign tax credit