Customer Service by Amazon (FBM) Disable/Enable?

Have anyone of you guys signed up for Customer Service by Amazon?

So I’ve been helping my friend with their Amazon for some time when they hit a rough patch. I noticed that when I looked at their listing it said “Sold by X” “Shipped by X” but “Customer Service by Amazon” which I thought was only an FBA thing but it’s on their FBM account. They also have no AtoZ that can be viewed in their account and they get little to no communication from buyers, like 4 the past month and they get thousands of orders weekly.

They have no idea how it was enabled and I myself never seen the feature or where to enable/disable it. Everything is shipped by Buy Shipping so winning/losing AtoZ is what it is, but not being able to see when and for what it happens with seems a bit odd to me if it’s hidden by having Amazon do the customer service.

Anyone familiar with this setting and the pros and cons for it? I doubt having Amazon handle customer service means all AtoZ are covered by them, but there’s literally zero INR claims for years on this account.