I haven't read McLuhan and have no opinion on his work. But from the article you linked to, the original phrase was "the medium is the message"
Your linked source also doesn't say anything about criticism of the phrase.
"The title is a play on McLuhan's oft-quoted saying "The medium is the message"."
"Why is the title of the book The Medium is the Massage and not The Medium is the Message? Actually, the title was a mistake. When the book came back from the typesetter's, it had on the cover 'Massage' as it still does. The title was supposed to have read The Medium is the Message but the typesetter had made an error. When McLuhan saw the typo he exclaimed, 'Leave it alone! It's great, and right on target!' Now there are possible four readings for the last word of the title, all of them accurate: Message and Mess Age, Massage and Mass Age."
Your linked source also doesn't say anything about criticism of the phrase.
"The title is a play on McLuhan's oft-quoted saying "The medium is the message"."
"Why is the title of the book The Medium is the Massage and not The Medium is the Message? Actually, the title was a mistake. When the book came back from the typesetter's, it had on the cover 'Massage' as it still does. The title was supposed to have read The Medium is the Message but the typesetter had made an error. When McLuhan saw the typo he exclaimed, 'Leave it alone! It's great, and right on target!' Now there are possible four readings for the last word of the title, all of them accurate: Message and Mess Age, Massage and Mass Age."