I agree. A sponsor could CHOOSE in this case between two processes : "Sponsor a spouse/dependent child" and "Sponsor your parent/grandparent".There is nothing preventing a person from doing that.
But what could he choose in the case of "Sponsor OTHER relatives" (looking at the subsequence of the list)? Or have he to follow the list?
Is it obvious that an adult child could be sponsored first and not an adult sibling or an adult niece? Or only if there are no siblings, neices, uncles and parents alive sponsor may sponsor an adult child?
Actually the whole thing is very confusing. First they are talking about undergaged siblings , then they say just "siblings" and in the end - "you could not sponsor your adult siblings". Does it work in the same way with adult children? it is obvilous you may sponsor your dependent children (under different procees but still under Family class), then they put just "son or daughter" under "Sponsor OTHER relative " process, and finally on the same page they say "you cannot sponsor your aduld child".
For me it sounds that you can sponsor any adult blood relative EXCEPT your adult child. :-X