Just the messenger...
I talked to the son this weekend and yes they/ the estate/ decedent father has/ had a probate lawyer/ had a will, and made updates in the months before passing as the estate was large and they had about 6 months notice (metastasized prostate cancer- if you're a male over 50 get checked annually).
Their will / probate/ trust lawyer has been involved since before day 1, and the heirs made priority lists of what they wanted/ didn't want, and are working out the details on who gets what. Some of the heirs brought in their own lawyers initially but it seems like all the issues, sans guns, have been amicably resolved. They are waiting on a final heirs agreement and a judge to give the final ok before property physically changes hands, but it's a pretty cordial settlement.
The guns were listed as something like a 'gun collection consisting of hand guns, rifles and related materials' so specifics listing gun models were not there.
Some items & interests were gifted prior to passing, which is apparently a significant legal event or action, but not all may not have been distributed. Real estate, life insurance and securities are the largest assets most of the family want proceeds from, and only a few of the heirs want any weapons, only 2 want the "fun"/ class 3 guns and that has been agreed to subject to legal transferability. He indicated the lawyer was not familiar with class 3 weapons which may have resulted in some of the initial missteps action that may have been questioned, hence the initial post here.
Apparently all of the CA questionable weapons were located at another home outside CA. So were other weapons that may not be CA friendly.***
There apparently was a discussion with their lawyer about the guns initially without any significance placed on class 3 and assault weapons, or the size of the collection. After the fact/TFL post, their lawyer found and contacted a lawyer who specializes in class 3 trusts & corporations. They are working to get all of the weapons legally transferred, as it was not clear but some or all of the weapons may have already been under a trust or corporation, which may make transfer simpler by changing or adding another corporate officer, beyond me.
Sounds like it is working out.
***I have no first hand knowledge if / when any of the weapons were found in CA, moved from CA at all, moved before or after death, or how or if they were transported/ teleported / deported / reported or were just plain ported
I am providing a 3rd hand ("double hearsay") update as requested for comment.