Since recently, Play Store is used for updates of Play services and itself. Apps app is used only for initial install and for updates of GmsCompatConfig.
GmsCompatConfig defines maximal supported versions of Play services and Play Store, Play Store won't be able to update them to an unsupported version.
If Play Store is unable to update Play services or itself, it'll try again and again after some delay. There's no way to disable this behavior AFAIK. Play services updates are considered very important by the Play Store, it'll try to download them even if auto-updates are disabled and device is on mobile data.