Yes, this is in Europe.
I think I learned quite a lot, namely:
- why I failed the interview (I struggled to produce correct code, the code wasn't very robust and I said it's ok to put it into production)
- why I haven't failed the interview (ex. no mention of my English language skills) - which was more valuable for me than the "why I failed"
- a fairly good confidence that there's little details omitted - when they submit you a voluntary feedback they may give just the most obvious information. Ofc I didn't get the data about what was said on internal meetings.
- some insight into their internal structure, opinions of individual interviews about me etc.
I probably burned bridges with that company but after the interview neither party was interested in cooperation so I decided to give it a shot and see what happens.
I had to wait exactly 30 (or 14?) days (GDPR deadline) for the feedback to get to my mailbox.