Phase shift of sample-and-hold

Hello experts,

I already posted this question up yesterday. But I think I posted in the wrong forum.

At the moment I am reading the blog of Dave Wilson

https://e2e.ti.com/blogs_/b/industrial_strength/posts/teaching-your-pi-controller-to-behave-part-vi

I can't understand the diagram of phase shift of a sample-and-hold in this blog.

The phase shift is caused by the delay time and you can calculate it very easily (see picture)

With a normalized frequency of 0.1 I have a phase shift of -36 degrees and not -18 degrees as the blog says.
where is my calculation mistake?

Thanks in advance - Bui