This is explained in Bug 20808270 - WEBADI NOT VALIDATING LEDGER and in Bug 20765340 - WEB ADI SPREADSHEET RESPONSIBILITY - RESTRICT LEDGER BY DATA ACCESS SET AND COA.
When attempting to upload journals thru WebADI, one of the users changed (hand typed) the Ledger name into the WebADI template, then added journals, selected upload, and the journals were successfully uploaded - to the incorrect ledger that was typed in.
The validation between the DAS and the Ledger did not occur.
This is the expected functionality.
It is not feasible to refresh the value of "Data Access Set" field as it is in context section of the excel sheet.
Adding an additional check and throwing error message for the scenario where user is selecting a different data access set with same COA and selecting a different ledger will limit the flexibility and restrict the functionality that application provides currently.
Though the data access set field is not refreshed in the excel sheet, internally application is honoring all the security aspects related to data access set.
"Please resolve the following error to continue.
The Data Access Set assigned to your responsibility uses a different Chart of Accounts than the one used when creating this spreadsheet.
To continue working on this spreadsheet, please relogin. Your responsibility must be associated with a Data Access Set that uses the original Chart of Accounts. "