Don't have my Note9 at the moment, but I'm sure this is related to S Pay, and handles highly sensitive tasks like randomizing your Credit Card number when you pay. And since when you tamper with Knox, Knox wants to lock itself down to protect your data... I can see why removing this app may cause that problem.
(And I HATE THE NEW ICONS. If I want a cartoonish UI, there's a ton of Chinese UIs out there.)