Are the collection challenge reward Dittos guaranteed shiny?

Hi everyone!

I was freaking out the other day because the Ditto from my collection challenge was shiny! I never had a background shiny before so I was hype. But then I completed the other challenge, and it was also shiny, so now I’m wondering if it was guaranteed. I also got another one in the research, so are they just guaranteed/extremely easy, or am I just getting super lucky? I was thinking I was “due” to get one after 3 shiny-less months, but if these are guaranteed, that’s a little less exciting.

Thanks!