But some, like Oppo and Vivo are--they ship with a Google-OKed copy of GMS, and redistribute the Play Store on their own app store as a way to install it (ostensibly for use when traveling outside the mainland, though it can also be used with a VPN). So clearly they are on some level Google certified.

However, they also contain switches to disable background GMS, which makes them almost de-googled. All of them, not just Huawei, have their own app store/updater, and have some sort of push notification to replace Firebase Cloud Messaging (as I understand, Tencent provides a one touch service so devs don't need to hardcode each OEMs notifications). Otherwise, it would be impossible to get apps or notifications without a VPN/proxy.