There are two Leshonos. In the first Lashon, we took for granted that the thickness of the tree stump doesn’t make a difference and the question is if Lavud helps. In the second Lashon the situation is reversed, we take for granted that Lavud is no issue but we are unsure about if the base is not thick enough.
After trying to learn that Kanim must mean Pachos Meshalosh, since Gudrisa would be like an Ilan — as long as we hold that there is no difference between them — the Shoal explains that there is a difference between a tree, whose stump is thick enough to be a Dyumad, and Gudrisa Dikanim, where only the top is wide enough. This difference is the basis of the question in the second Lashon.
The Shoal is responding, just like you don’t think Kanim and Geder are the same, since you differenciate between Lavud and Lavudless, I too differenciate between an Ilan and Gudrisa Dikani.
The second Lashon follows the same logic path with opposite assumptions.