Elon Musk, in the Starship announcement, talked a little about un-designing in response to an interviewers question.

“How did you go so fast?” asked the interviewer.

Umm, well; I have this mantra called “If the schedule is long it’s wrong. If it’s tight it’s right.”

Yeah, and basically just go recursive improvement on schedule and said with feedback loop “Did this make it go faster?” Ok. If it didn’t we’re going to need to fix it. If the design takes a long time to build, it’s the wrong design. This is the fundamental thing. Over and over it’s like the tendency is to complicate things. 
I have another thing which is: “The best part is no part, the best process is no process.” It weighs nothing, costs nothing, can’t go wrong. So as obvious as that sounds: “The best part is no part.” The thing that I am most impressed with in when I have the design meetings at SpaceX is what did you Un-Design? Un-Designing is the best thing. Just delete it. That’s the best thing. Yeah.

Elon Musk, 2019

Is Un-Designing scope-creep in reverse?

Distilling the purpose of a project to its core. Eliminating extraneous expectations. On every iteration.

How do you justify simply deprecating a feature because it is fragile, expensive and underutilized? Where do you draw the line and how do you inform your customers?

On a rocket, the bar to meet is tactile and directly related to vehicle safety and reliability.
In software, there are more competing stakeholders.