angela Many people have said over the years Airplane mode doesn't really turn everything off.
To be clear, on modern phones with Wi-Fi, airplane mode often does not turn Wi-Fi off. It also may well not turn Bluetooth off. I suspect it does not turn NFC off. So a claim that "Airplane mode doesn't really turn everything off" is true and easy to verify.
Also, to be clear, there are fairly-credible reports that in the past malware has been manually implanted on individual phones to transmit audio when a phone appears to be off (source). Once piece of good news is that GrapheneOS has pretty good resistance to persistent malware, which means that rebooting has a high likelihood of removing malware from a device running GrapheneOS. That said, somebody concerned about being individually targeted by state actors should seriously consider getting expert advice from a professional security consultant (as opposed to YouTube videos or forum posts by anonymous users).
I absolutely agree that most GrapheneOS users don't personally have the training to measure whether or not a cellular transceiver is receiving or transmitting. Each user needs to find some way to decide what to trust. Some users may choose to trust what's already on the project web page. Other users might not trust anybody except for an expert they personally hire.
angela Now Graphene OS indicates "airplane turns off everything" and we as users have no way to measure and test that.
I think the FAQ entry on the GrapheneOS web site claims something much more precise: "Activating airplane mode will fully disable the cellular radio transmit and receive capabilities".
angela Do normal Android phones turn off all cellular telemtry in airplane mode? I have heard over and over again that such things are not true and pings still occur but just much less frequently.
There are probably hundreds of models of phone in circulation today. I don't know which would be considered "normal Android phones", or how to support a claim about what all of them do or don't do in airplane mode.
I think the GrapheneOS web site intends to limit the claim about cellular activity in airplane mode to Google Pixel devices that GrapheneOS runs on. I also think that on the GrapheneOS user forum it might be best to focus on any potential evidence that for Google Pixel phones in airplane mode "pings still occur but just much less frequently". If no evidence can be presented, some people might choose to accept the clear statement (no transmit, no receive) on the project's FAQ page. Other people might choose to hire an expert who they feel they could trust.
Or, I suspect, 90% of GrapheneOS users live under 50 miles from a university with an electrical engineering department. These days many electrical engineering departments have enough equipment to scan for emissions in various cellular bands. So it might be possible to obtain an expert opinion for free.
Some alarming claims about cellular-network surveillance are alarming and can be supported by evidence. Other claims are alarming, and could be measured, but are circulated without evidence. That seems irresponsible, because circulating alarming claims without evidence has a tendency to alarm people. The responsible thing would be to do the measuring so the alarming claim could be circulated with evidence.
Without personal expertise it's hard to know what to make of claims found online. But there are things that can be done. One thing is to collect the claims and ask a nearby person who does have expertise. If one encounters a claim that "pings still occur but just much less frequently", one could ask somebody who repairs cellular phones for a living if that person has observed that phenomenon, or ask an RF engineer to check whether it happens for one's personal phone. None of us can be an expert on everything, but all of us can consult an expert we feel can be trusted. It is not necessary to just live in fear.