Why do phone numbers and delivery instructions not sync from Xero to ApprovalMax?

Why do phone numbers and delivery instructions not sync from Xero to ApprovalMax?

Although you can add in Xero phone numbers and delivery instructions as contact delivery details, these fields won't be synced to ApprovalMax due to Xero API limitations.
If you need to specify phone numbers and delivery instructions, you have to do it manually in each Purchase Order and also when using the Copy Purchase Order functionality.