Yes the lions share of the backup content is “uploads”.
However a backup is not complete without the “uploads”.
My personal target is to move the images / “uploads” to Amazon S3 to avoid this issue for this specific instance, however there is still some testing to be done on a high topic / post count instance before I can trust the migration to S3, some issues already highlighted in that thread (more specifically avoiding a rebake of all posts).
I have other Discourse instances that would benefit in the backups being created in a more streamlined way.