It's probably a specific issue on your flight as the A321 and A321 neo have very similar dimensions (https://www.aviatorjoe.net/go/compare/A321neo/A321-200/), so possibly your BER-AMS was loaded with a specific cargo that might have weighted a lot and needed special care when unloading. It could also explain the loading issues in BER!

But I've taken lots of A321 flights with AF, and this has never come up. I don't see why it would be different (in general) with a KL A321.