that was not a vote by 2/3rd but it become a vote by majority
as un members decided its not important enough to be a vote by 2/3rd and rejected USA proposal
by the way let look at the un charter
en.wikisource.org
more exactly at article 6
what happened to Taiwan is not applicable here in that they didn't throw out a member they gave its sit to another group that they believed represent the land and country better , now go and try get that recommendation about Russia from UNSC if you can
in short article 18 you quote only become to effect if article 6 come to effect first