Oh no. I mean if you create a custom section in shopify, someone will use that section in the theme customizer for their website.
What I mean are these sections,
And as you know, I can use Rich text section in my website however many times I want (That is what I mean re use. In user perspective, not a developer perspective) . The section.id part makes sure each of those rich text sections has a unique ID so if I ever wanted to apply CSS styles for the first Rich text section, the others are not affected. Same goes for javascript. I can target each section individually.