If you end up not getting and offer please notify HR at the ECB. I have been part of recruitment and this is absolutely not how things are done at the ECB normally. HR should follow up with the HOD of the area. This is not acceptable.
I am aware of other strange recruitment processes in the past, for example some campaigns fixed, and despite people involved hr nothing happened. Unfortunately people at ECB can do whatever they want, using ecb for personal interests in this things. I can remember a campaign where the hiring manager hired her supposed boyfriend who was definitively a donkey in banking supervision for having him in FF