The article actually states that grass fed and organic chicken are the best ways to get collagen but not the only way but doesn’t cite any research that ingesting collagen benefits skin. I like Dr. Mercola but anyway, I did a google search and came up with one research article suggesting that collagen supplementation from marine sources can help with a number of skin issues: https://www.hindawi.com/journals/omcl/2016/4389410/abs/.
I think researching to back up statements is very helpful for all of us. Or course it is time consuming.