There were also reports of sub-standard brittle Rivits and brittle steel that was used in the construction of White Star Lines RMS Titanic.
The rivet theory is interesting, but given the stress when the ship hit bottom, not sure how it could ever be established.
Unfortunately, it seems likely it will never be known exactly how the iceberg opened 5 compartments to the sea. The underground forward hull imaging didn’t show anything big enough to be visible there, iirc.