One of my apps is allowed to use the mobile network, and all others are confined to wifi. This is specified in my Data Saver settings, but according to GlassWire, Google Play Store is still using the mobile network. Any suggestions on how to confine Google Play Store to wifi are welcome.
Google Play Store and Google Play Services self update is known to update when they "want" no matter if you are on WiFi or mobile and what settings you have configured.
I am not sure if the respect data saver settings but as Google Play Store is a system app permissions and settings do not apply to it.
And you have agreed to those updates when setting up your device. The following screenshot is from the setup-wizard that shows up on a new device/after a factory reset (see section marked in yellow).