Grey recognized what was going on right away. This was a step that every single one of his apprentices had been through at their coming of age. Most dwarves would experience an epiphany in their life based on what their crafting system was. It was common for them to finally connect all the dots between what they could do in the future and what they had seen. It was a completion of all of the processes coming together to an end goal.
"Hit the metal harder! How can you shape that if it pushes you back harder than you push it!" Grey didn't let up on Walker in the least. He had treated every apprentice this way during the epiphanies they had in their training. This was a step that allowed them to push to greater heights in their skills and would help in their specific systems.
Walker is feeling the forge and the forge is feeling him. Glad he is finally learning some forging skills.