The thing about NOTAMs is that the person writing it can specify whatever speed they want. You must have the performance in able to follow it. If it says you need to cross at 280knts, you need to cross at 280knts. There’s no ambiguity.
Crossing restriction — A directive issued or published by air traffic control that instructs the pilot to cross a given waypoint at a specified altitude, and sometimes at a specified airspeed.
1. “Crossing restriction” on Aviation Glossary