You don't just delete stuff… it's more that your pull requests remove more lines than they add. But I'm sure the person you're replying to is exaggerating, or they got promoted because of completely unrelated reasons.
I find it’s less common for me in ruby, even refactoring bad ruby. Sure I can remove lines but bad JS/React balloons so fast.
My current org values this and my direct boss constantly praises those of us that try to remove more lines than we add. Very refreshing.