this is true of google android and iOs, however I understand it is NOT the case for graphene OS 

 but you have verified gaussmeter evidence that it is true? 

 I don't think you'd use a gaussmeter but rather a mobile base station so you can measure the incoming pings

This was the approach used by SRLabs when testing their Blue Merle software for IMEI switching

https://github.com/srlabs/blue-merle?tab=readme-ov-file#imei-randomization 

 doesn't necessarily have to be mobile radio protocol, just something that someone can pick up, doesn't have to be strong, about 20 metres is probably enough, and that won't detect it 

 nostr:nevent1qqs94y89u595tq4yaff4c20ne4slapdplkaxr3d3uxscg2ssnxqr45qpz3mhxue69uhhyetvv9ujuerpd46hxtnfdupzppx7umn8dedmv7626nsy9nmse0vxsy24mdf4jshuc6s9xwzc5ujqqvzqqqqqqyh7s4nj 

 Carrier pigeons solves this  

 The only way is to remove the battery, which was easy on cell phones 20 years ago. Now the quickest and easiest way would be to destroy the phone