Red Dimmers - Some secure and some not. Why?

So, some of my Red Dimmers include secure, and some of them include non-secure. There is no rhyme or reason. It’s not like there is an upstream non-secure device, or the order they are included. Has anyone else seen this behavior?

I have 10 Red Dimmers and 5 Red Switches. 5 of the 10 Dimmers right now will only include non-secure.