Radisson does say coat without tie is suitable as informal. However, wasn't the tuxedo developed as "informal" attire? Wasn't it designed to be more comforable that "tails?"
edited to add:
Here is what I found on history of tuxedo:
1886
The first Autumn Ball, held at the Tuxedo Club in October 1886, is marked as the official first appearance of the Dinner Jacket. Then, it is said Griswold Lorillard and his friends startled the people attending the Ball by wearing a scarlet satin lapelled Dinner Jacket, without tails, while all others were attired in the traditional white-tie and tails. And thus was born the elegant garment forevermore to be know as the 'Tuxedo.' The tuxedo was adopted by people rich and poor as the symbol of celebration, good times and special occasion. It was designated by the motion picture industry as its symbol for high society, class and elegance, and the tux even became a symbol of hope for better days during the Depression Days of the Thirties. And, it was defined by the tastemakers and standardbearers as the appropriate garb for those events in an individual's life when only a tradition of elegance will do.
