I think you are correct. Affects Roman Catholic interpretations but not Protestant.
AFAIK, Roman Catholic interpretations have never insisted that Mary was perpetually virgin. Never the less, the other offspring of Mary would be half-siblings at best in the eyes of the Catholic church.
Incorrect as regards to Catholics. Catholics do not believe Mary remained a virgin all her life. Correct that Catholics, unlike Protestants, don't believe Jesus had younger siblings. The author of the article doesn't really understand Christian dogma, regardless of denomination.