they set the standards for what they considered to be a safe clearance of obstacles for design of instrument procedures.
.. and of no relevance to takeoff ..
Excuse me... this is of HIGH relevance to the all engines operating takeoff.
This example won't kill you, if you do not comply, but will get you into trouble with the air traffic controller.
Replace "due to airspace structure" with "due to mountain in departure path", and you get into more serious trouble. And it might not even limit you in your takeoff (engine out) calculations, as the SID might take you OVER the mountain and your engine failure procedure might take you in another direction with no significant obstacles.
In the example of Cologne, you have 3815 meter (12516 feet) runway. SO your takeoff performance calculations might give a result with so much derate/assumed temperature thrust reduction, that you are unable to met the 15.2% climb requirement for all engines operating.
This is from experience, not assumption. In this case you have to select MORE thrust to comply with the SID, than required for the engine out procedure. Your performance calculations won't warn you of this, as the software doesn't get any information about what SID you intend to fly.
So YES the procedure gradient is of HIGH importance to your all engines operating takeoff.
Here is the example:
