Using either contact or journey data can be critical when using decision splits. But how can I find out whether a contact or journey data attribute was chosen, if attributes have the same name? The view only provides the attribute name, not from which source it was taken.
You are correct the details of an attribute in a decision split is limited when viewing in an active Journey. If you view the same decision split in the draft of the Journey you'll be able to see the path for each attribute.
See the example below where one path selects the emailaddress attribute from the Journey data (in this case a data extension) and the second selects Email from the contact synchronized data extension from SF CRM.