Hold up bro. The only thing you've ever posted on HN - and you posted it a lot - is that you never put a SIM in a phone.
Granted, when it comes to mobile phones I whinge a lot because I reckon that users have been screwed terribly by both telcos and the likes of Google and Apple. By any measure, users have certainly come off second best.
Your point about this matter being the only thing that I mention on HN is simply ridiculous.
For others who may perhaps read this, the only thing I can say in my defense is that if you actually read the contents of my previous posts then you'll note that the subjects I comment upon are both varied and quite diverse. :-)
I would further add that as a comms person I work with phones regularly, for this I have separate test accounts and in some instances SIMs are used in them directly (especially if one is testing the phone's wireless circuitry etc.—obviously without a SIM[1] you cannot fully test the device). Nevertheless, such phones are nearly always rooted and have GApps removed (or otherwise have them disabled/hibernated).
BTW, I like people like you who actually take a rigorous approach to what people say and take the time to cross reference their various comments. It's even nice to know someone has taken the time to read what I've written.
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[1] For testing I also use 'dead' SIMs (ones whose telco accounts are now defunct) as well as prepaid not-yet-activated accounts. Often 'test' SIMs are useful for checking the phone's GSM/HSPA/LTE electronics (as limited communications can even established with the telco). Using SIMs that are incapable of carrying normal data traffic has the advantage that the phone can be tested without information such as its serial or IMEI number being sent to Google. (And occasionally I've even asked telcos to disconnect both data and SMS services to avoid 'accidents'.)
I would add that if someone wants me to either maintain or root his or her phone and the owner has yet to provide me with a working SIM (which happens often enough) then I do so with one that cannot access or send data across the internet. As I see it, I don't have the right to link someone's phone that doesn’t belong to me to any other account or phone number that does not belong to the owner.
... and SIM has valid certs, GPS time is synced to few split seconds, your eNB tower-your Uu up/down freqs, timeslots are assigned and mutual auth is passed, cyphering(can you believe it? "encryption" and "cryptography" are apparently deliberate word choice to light up normies, "they" proper say "cipher") is set up, HSS(heard those are Oracle DB) through MME is accepting your IMEI + IMSI + credentials, HLR has your location, VLR has you mapped to operator's home EPC if you're roaming, your IP address is assigned(LTE is all IP), PCRF is configuring your QoS stuff, S-GW is routing your packets to P-GW, your IMSI-IP map is sent to SMSC and SIP sessions for VoLTE call signaling as well as for SMSC is up, your BS(eNB) is maybe aware of your location, speed, direction of your movement for handover purposes, and by the way one of many accounting database somewhere in there probably a table referred to by HSS says your contract is not valid as far as it knows when and only when you try to request something paid. (I'm pulling these all out of my curious nerd memory so lots might be missing, outdated or unbalanced.)
So yeah testing a phone with testing SIM works... Just a few dozen Oracle Cisco Huawei Ericsson Nokia Alcatel gears has your everything in the database.
I am in no doubt that the moment a SIM is inserted into a phone and it's switched on that the activities you've outlined happen—and all that gear you've mentioned then "has your everything in the database". For my purposes, that all that gear has soaked up info is essentially irrelevant (as it's going to happen anyway the first time one makes a call).
If I was being rigorous (or up to some nefarious mischief) and did not want any of that data to leak (at least until I was ready) then I'd disconnect the phone's antenna and/or conduct the work within a Faraday cage to stop the the radiation. Also, there are other details and steps I'd take but I'll deliberately refrain from mentioning them.
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* "I'm pulling these all out of my curious nerd memory so lots might be missing, outdated or unbalanced."
Ha, right. Then even if you're not fluent, I reckon you'll be familiar with all those books/standards that deal with such matters—ones that just about put Encyclopaedia Britannica to shame. Seems to me no normal human (even propeller-head nerds) could retain all that detail. :-)