Never seen it on the 777, but as one of the first modern jets not to require “3 degrees per second”, this is not surprising.
An initial target pitch would only be valid for a specific Vr, rotation rate, and 'standard power’.
1) Having experienced close to 5 degrees/second and less than 2, from the same runway with similar weights, the final 'correct' pitch was very different.
2) What is standard power? Who knows, but the resulting acceleration will be a factor for the pitch target. Are you at max assumed temp, and lighter than normal?
Targetting a specific pitch for takeoff could well be a “children of the magenta line” problem in the making.
It's critical that Type Training includes the correct rotation technique, 'towards a target pitch', adjusted to achieve V2 + 15. The buffer of 15-25 assumed that you had excess energy, and that the climb gradient would not therefore be compromised.