During iCloud account recovery, you may be asked for credit card details that are actually verified by running a charge, causing issues even with correct information.
Securing your own email account can involve user-controlled methods like two-factor authentication with a physical token, whereas iCloud's security measures are more restrictive and dictated by the service provider.
Recovering an iCloud account might involve providing credit card details, which are tested by running a transaction, leading to potential issues if the card details change.