I believe even 3G supports mutual authentication (at least if the SIM supports it, i.e. it’s not a very old GSM only one), but anonymized identifiers only appeared with 5G.
and yes, that only prevents the lower denominator which uses downgrade, which is the vast majority everywhere.
\*\*You can include asterisks if you escape them, like \*: *#*#4636#*#*.
I know that setting, but I'm not entirely sure if that controls a preference or a mandatory cell config, and if it will prevent downgrades from the network side or not.
Some manufacturers and most custom ROMs also seem to offer that option without a dial code, but I haven't found any documentation about that feature yet to be sure it actually forces the modem configuration. I've found mentions online about this setting being changed without user interaction, so there seems to be a mechanism on some phones (carrier-branded ones maybe?) that alters this config.
having the ui it not is a balance between playing nice with over reaching law enforcement and enterprise clients.
if you don't have an extra $400-900 and buy a cheaper android, you get to dial ##4636## (hn screws asterisks, look it up) them go into phone info, select each sim radio and change the drop down (and hopefully you know all the standards by all names to make the right choice. hint 5G is NR there)