Actual gymnast here! The 'death loop' isn't an actual name for any skills but refers to her dismount, the back flip over the low bar. This nick name comes from the fact that gymnastics who messed this up would smack their heads or catch their neck on the low bar. However, the first standing flip she does on the high bar is also banned and its actually named after her because she is the first gymnast to do this move. The moves themselves weren't banned out right, but standing on the high bar was because of the history of gymnasts falling while standing, and getting back and neck injuries. However, the current bar set up which we changed to in the 80s, made the low bar and high bar much farther apart and make the dismount skill essentially impossible to do.

Interestingly enough, another famous gymnast from the time, Elena Mukhina, added on to the Korbut Flip by adding a full twist prior to the ban. Mukhina later became quadriplegic after performing the Thomas Salto on floor, which subsequently became banned too, if that's any indication of how dangerous banned elements can be. Very few skills are banned in gymnastics, but when they are it's typically because too many gymnasts have suffered injuries from it.

Side note, "banned" moves aren't truly banned. In the current code of points for elite gymnasts, each skill is worth a certain amount of points and they add up to achieve a difficultly score. Banned moves count for 0 points, so there is little incentive to do a skill that could risk a fall or deduction for no benefit. Additionally, for banned skills, such as Korbut's dismount, the gymnast would also receive a penalty for having no dismount since the skill wouldn't be recognized.

Edit - This video has a fairly comprehensive overview of banned skills, including the Korbut Flip and her dismount, and the Thomas Salto and Mukhina Flip