The 1500ft comes from the OPS1 requirement to consider the takeoff phase up to 1500ft AGL. From then on, it's under the enroute climb requirements.
When Flypgrestanda say 'no note' that means there is no emergency special procedure and the performance in based on runway track up to 1500ft AGL. That ticks the takeoff performance box. From then on, you're on your own...
Erik.