That's not gow it works though. The way you describe it the original account should have the outgoing payment to the merchant. An incoming from the new account and an outgoing one on the new account.
In reality any record of the payment disappears from the original account and the new one just shows the payment to the merchant. With a time and date that will not match the actual transfer to the merchant (could be weeks apart).
As I see it the dates are "fake". There should be a record of the original payment, and as Bunq is a bank, I consider this a big problem. And am frankly surprised this wasn't immediately fixed when I and others first reported it, or alternatively they could even have rolled back the functionality until fixed.