Yes, Stress relieve is advised.
I had good sucess with hanging long thin blades vertically in the HT oven. This minimizes warp by handling the heated blades. They become quite floppy when hot.
Also you have a short window directly after the quench for straightening. I clamp the still warm blade between two flat bar of steel and let cool to room Temp for 15-20 min. This usually results in a perfectly straight blade.
I do most of the grinding before HT because its quite easy to overheat such a thin blade when grinding ,especially the edge and tip area if you are not careful. As said by others , slow speed on the grinder, fresh belt and dunking after each pass will work. Thicker blades have much more mass to conduct the heat away from the edge and tip area - thin blades overheat much more quickly when grinding and its easier to ruin a blade that way.
I once saw a video from the factory of the german brand "Windmühlen" kitchen knifes. They are known for their special ultra thin grinds which are still done by hand. The blades were ground after HT but they did this on very big, slow moving waterwheels.