They are not denying that a design fault (eg in the handle or safety pin) might have caused the ejection. However, since the ejection should have been survivable, the fatality was due to the failure of the parachute to deploy. As soon as the over-tightened bolt was discovered, therefore, MB could issue that statement to reassure their customers without needing to establish why the ejection had happened in the first place.
Well to a Layman, that reads as two design faults, one allowing the pin to be incorrectly fitted and one allowing the shackle to be incorrectly torqued, if it isn't a design fault then why are the RAF / MB looking to replace the bolt with a shouldered bolt to correct the issue, as a rewriting of the maintenance procedure would rectify it.
Sphlc read 134