Larrin addresses the carbide type in 204p class steels and why they are easier to sharpen:
"Microstructure
The high chromium content in M390 means that less of the high hardness vanadium carbide is present in the steel, and the majority of carbide is the lower hardness chromium carbide. The vanadium does increase the hardness of the chromium carbides, however. You can read more about the interaction between different elements for carbide formation in this article on carbides. Chromium carbides tend to be larger than vanadium carbides in power metallurgy steels which limits toughness, but they are easier to sharpen because they are softer than common sharpening abrasives like aluminum oxide. Bohler reports that M390 has about 18% chromium carbide and 2.5% vanadium carbide [20], and in my metallography I found about 22% carbide. This high carbide volume results from the high carbon and chromium in the steel, which puts its carbide content similar to steels like Maxamet, S90V, and 15V. The high volume of chromium carbide means that M390 has a larger carbide structure than those steels, however. Stainless steels with a lower carbide content like S35VN, S45VN, or Vanax also have a finer microstructure. You can compare with many other steels in this article which contains all of my micrographs."
Citation from:
https://knifesteelnerds.com/2020/06/01/ ... -and-204p/
For what it's worth I too find it much easier to sharpen than the steels with more vanadium and tungsten carbides. That being said, proper stones and technique make any steel "easy to sharpen", some just take a little more time
