The difference is at 25000ft ....

 

An operator shall not operate a pressurized aeroplane, above 25 000 ft, when a cabin crew member is required to be carried, unless it is equipped with a supply of undiluted oxygen for passengers who, for physiological reasons, might require oxygen following a cabin depressurization.... for 2% of passengers...

 

Oxygen masks for use by flight crew members in pressurized aeroplanes operating at pressure altitudes above 25 000ft, shall be a quick donning type of mask.