Consider an Android app that does no network I/O: It links to no HTTP libraries or any third party libraries at all, does not request INTERNET or ACCESS_NETWORK_STATE permission in the manifest, and uses no advertising software.

Yet after uploading an App Bundle to the Google Play Developer's Console, the Pre-launch report's Performance section reports on network bytes sent and received from one or two of the test devices!

The detail report for this App Bundle shows just one spike of network activity at 4:05 into the test run, where it claims to send 400B and receive 818 bytes. The recorded screenshot video shows nothing changing on screen at that time.

The app has an TextInputEditText field, so one hypothesis was that this field was accessing a spell-check server, but the field gets accessed earlier in the test run, not at 4:05, and it has spell-checking disabled.

• What code in the test device could be doing network I/O, in this case on Samsung Galaxy S9 and not on the other test devices? (With an earlier App Bundle version, both Samsung Galaxy S9 and Xiaomi Redmi 6A did some network I/O.)
• Is this happening from Samsung extensions to the Android OS?
• Is this just irrelevant network I/O from an independent process such as the test lab communication?
• Any other hypotheses?