Not sure if they do or not, but they could just build two separate versions of the app against different services. So, if you're publishing to the Google store you use gservices and if you're publishing to Huawei store then you use Huawei ones. The API could be the same from app's perspective, so it'd just be a matter of which library you use to talk to the services.
Okay but doesn't that necessarily also mean that it doesn't work with their own back-catalogue of apps? Do Huawei apps still work on Google-Android?
Not sure if they do or not, but they could just build two separate versions of the app against different services. So, if you're publishing to the Google store you use gservices and if you're publishing to Huawei store then you use Huawei ones. The API could be the same from app's perspective, so it'd just be a matter of which library you use to talk to the services.