Why i cannot make changes to revenue scheduling in AR invoice - before create accounting

I have a business scenario - When i create an Invoice manual or Imported - why an AR accountant can modify the revenue scheduling rule but it impact does the overall behavior of the invoice accounting.

e.g AR accountant creates an invoice with a deferred contingency rule and "just saves" the transaction (not completes) before running the create accounting process he has the access to change the revenue contingency rule but it has no impact to the revenue accounting?? in short the revenue accounting is triggered based on the rule selected initially and no matter what (you change it or not) the accounting doent change