Found an article by Kato Masafumi on Nobunaga's castles Komaki, Gifu, and Azuchi. One main point the article hits on Komaki Castle. Yes, it was a dry run for Azuchi and had stone walls. However, Komaki Castle was located on an independent hill, like a floating island in the Nobi Plain. Komaki had no huge hills or earth base. In other words, it was defenseless.