It's interesting to note that Muhammad also taught that a lot of other historical figures were prophets too, e.g. Alexander the Great.
Citation needed. This is a fallacy that has been spread unfortunately.
Furthermore, note that even what is mentioned on that page is speculation from certain Islamic scholars. There is absolutely no authentic Hadith (or even non-authentic as far as I know) that mentions Alexander by name. All that is mentioned in the Quran is the "Two-Horned One", which could be Cyrus as mentioned on the wikipedia page, or it could be someone else completely.
One last point, the person in question here was never declared to be a prophet in the Quran as you claimed, but just a righteous king and person.
Online society's attitude to Wikipedia seems to have settled into two camps; those who refer to it as an authority and those whose avoid it due to negative experiences with inaccuracies or politics.
I'm trying to move from the second group to a third; patch-up articles for the benefit of other people.
I will take your advice into consideration and attempt to amend that page. I don't know what the monitoring procedures are on wikipedia, and if they will allow such changes to persist.