I've taught C at university level, and used to give crash courses to new college grads and interns in industry.
The one thing I impart the most from the beginning is to develop good instincts for secure interfaces. You should be able to look at function signatures and see alarm bells for unsafe practices. For someone skilled at C this is second nature, you can see bad practices from a distance, often at the function signature level.
It's unwise to neglect it in the long run. It's perfectly reasonable to ignore it initially. There are different valid pedagogical approaches here. Your approach may be suitable for the type of student you were interacting with, but the profile you're familiar with doesn't represent every person who might be interested in learning C.
The one thing I impart the most from the beginning is to develop good instincts for secure interfaces. You should be able to look at function signatures and see alarm bells for unsafe practices. For someone skilled at C this is second nature, you can see bad practices from a distance, often at the function signature level.
I think it would be unwise to neglect this.