There are in the correct alphabetical order by country. That user is probably suggesting them being in order by denonym, making Congolese and Burmese in the wrong spot.
Imagine my surprise at discovering that the people of Kiribati are not called Gilbertese (per JetPunk)! I think that's the proper English demonym (as opposed to I-Kiribati in the local language, which is ... Gilbertese!).
In addition to the interesting ones you mentioned that somewhat unexpectedly add "ian" suffix though, there would be a good number of less interesting countries whose name ends in "ia" already in such a list.
I tried Sri Lanka for Sinhalese, but it didn't work. After, I looked up Sinhalese and it turns out they're a group of people in Sri Lanka, but not the entire population. The more you know!
Cool quiz, I only missed East Timor and just squeezed in Myanmar at the last second, having been stuck on the last two for ages. Feeling quite pleased I knew San Marino though!
https://www.jetpunk.com/user-quizzes/1272735/countries-with-an-ian-demonym-not-ending-in-ia
https://xnepali.net/nepali-or-nepalese-what-is-the-difference/