Interesting. I'm not an security expert, but believe locking SIM card with a PIN code is a reasonably good idea to ensure in case of a stolen smartphone (non-targeted) it would be more likely thrown out as useless rather than used for any nefarious purposes.
SIM card PINs are not discussed in the article. Instead they recommend asking your telcos support rep to attach a note to your account to prevent sim swapping, which doesn't work.
Or I'm wrong?