Here, "accountable" is really an industry jargon, and means neither reporting nor responsibility but merely the need to take into account in planning and calculations. The reason why an engine failure need not be considered below 300 ft is because it is overridden by more stringent provisions in airworthiness requirements for multi-engine aircraft - the plane's ability to continue takeoff and initial climb with one engine inoperative ("OEI") should already be guaranteed no matter what, otherwise the aircraft cannot be certified as airworthy. (Being a pilot, I just happen to know this off the top of my head).
Of course, one can translate it in a simpler way, like "...ist zu betrachten"

Honestly, German isn't my working language, I merely dabble in it, but aviation is certainly my field :-)