Is there any negative side-effect of doing this with a single journal?
The intermediate account would be an asset account? Do you know the name that is typically used for that account in English or French?
I agree that it is a good idea to use the intermediate account if the payments are in bank limbo overnight or more than one night. In some countries it still takes 2 or 3 nights to make a payment between two different banks. If the payment crosses the boundary of a financial period then it is not in either bank account on that night.
However, if it is a payment between two accounts with the same bank and the bank completes it within 5 minutes or less, I feel the case for an intermediate account is not so strong. E.g. all the UK banks do something called Faster Payments now and it is almost always the same day.