Yes, Chrome sync is sort of a thing of its own, as it's meant to carry settings across environments where you use Chrome whether or not you're using any Google Service at the time. It's the same as Firefox Sync in that regard. You really have to think about what a thing is doing. I could be mistaken, but I think you can "Sign in to Chrome" (which is how sync is handled) using an e-mail address that's not even affiliated with Google at all, but I'm not 100% certain about that.
Browser settings (and other bits that are browser specific) are connected via a sync or Chrome sign-in account. Google Services - gmail, youtube, calendar, drive, hangouts - are all attached to a Google Account. Though, of course, many people use their Google Account e-mail as their Chrome sign-in id, it need not be that way. When I was testing out the ability to use multiple Gmail accounts within one browser my Chrome sign-in remained untouched. The same is true in parallel when I log in to more than one Gmail account in Firefox my Firefox sync account remains untouched. The purposes of a services account and a browser (note, browser - not Google Drive) sync account really need have no overlap.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1803, Build 17134
Memory is a crazy woman that hoards rags and throws away food.
~ Austin O'Malley