doesn't moving the creation date forward in time make you vulnerable?
if you create some content in 2018 and I rip it off in 2019 and then you update your copyright to 2020, what's to stop me from saying I came up with it first?
That's partly why you have a span like "Copyright 2018-2020" - you are saying some of this material is older, some isn't. You need to keep copies of the older version with the older copyright to be clear which parts were invented when.
I want to like that idea. Unfortunately, I can counter with: When you (as an outsider) see two very similar projects, one claiming to be from 2018 the other from 2020, what will you look into/try out first?
if you create some content in 2018 and I rip it off in 2019 and then you update your copyright to 2020, what's to stop me from saying I came up with it first?