It's probably an error in the registry. It was introduced by Suttons and they describe it as being around 30 inches tall. If I had to guess, Anton Mego probably registered it with a height of 76 cm (76 cm roughly equals 30 inches) and it was mistakenly entered in the registry as 76 inches. He is from Slovakia, if I remember correctly, and it would make sense for him to use centimeters rather than inches.
All that being said, I have a TB seedling that routinely reaches 5 to 6 feet, so 76 inches wouldn't be impossible.
It would be surprising to see an iris of that height registered, though. The taller they get, the more challenging it is to keep them upright.
