It seems the author is already kind of biased when he set out to analyse the data.. use of the term 'overzealous vegans' in the first paragraph sets of a few alarms for me.
I think it would be interesting to look at other long term studies (like the 7th adventist study someone else mentioned here) as well as studies that look at plant based eating as a cure/preventative method for more specific/acute diseases (like Dr. Caldwell Esselstyn's WFPBN solution for cardiovascular disease, or Dr. Greger's 'How Not to Die' which compiles and summarizes research in the WFPB space https://nutritionfacts.org/book/)
I think it would be interesting to look at other long term studies (like the 7th adventist study someone else mentioned here) as well as studies that look at plant based eating as a cure/preventative method for more specific/acute diseases (like Dr. Caldwell Esselstyn's WFPBN solution for cardiovascular disease, or Dr. Greger's 'How Not to Die' which compiles and summarizes research in the WFPB space https://nutritionfacts.org/book/)