With LibreTube that’s only partially true. It doesn’t sync with YouTube, but LibreTube on Android will sync with your favorite Piped instance on desktop, so if you also browse YouTube on desktop using Piped, you’ll get that experience of a synced subscriptions list. You can use Google Takeout to easily migrate from the main YouTube to Piped with all your subscriptions active.
With NewPipe you’re correct - there’s no sync. You can import from Google, but there’s no mechanism to sync with a desktop version.