Ok, I see your point but the behaviour of Obsidian is not coherent. In fact, if you check a checkbox in preview moede, Obsidian automatically strikes through all its sub todoes.

As you see in image, it doesn’t check them, as I request here, but it still strikes through all its sub todoes and strikesthrough means that you have done that todo.
So, Obsidin should behave like I requested or it shouldn’t even automatically strike through all its sub todoes.
I don’t like this behavior but you shouldn’t like it either.