Why does Google's Rich Results test find structured data that I don't see in the browser?

Using https://search.google.com/test/rich-results I ran a test on this web page: https://www.cwcycles.co.za/product/sram-pc-gx-eagle-chain

It returns a found product, and on inspecting where that structured data is located it shows that there is a JSON-LD block in the head element:

However, when I view the source for this page in Chrome there is no such block. Additionally I have inspected the page in the dev tools to see if JS is building it, and I have also changed the UserAgent to be GoogleBot, but still no luck in producing this JSON-LD block.

Why is it that Google's tool is seeing it but I am not?

Note: Originally I discovered this issue in a Python tool I have built, but have replicated it in the browser for ease of asking the question.