Anyone know the law on this?  Are they unrelated and this is just wishful thinking?

Not asking about NYC, but just the rest of NY.  Also not asking about intent, just possession.  Yes I know anything is an illegal weapon if you use it that way.

Butterfly knives dropped off the list a couple of years ago

Thanks - is that the Penal code list you're referring to?  Is that just for possession or can they be carried as well?

The law doesn't have a list of things " that can be carried"
It has a list of enumerated items that are prohibited to possess unless you are considered to be exempt

Butterflys do not lock in place when opened, you manually have to close the clasp to lock it open so that is how they get a pass here. Attached File

You said they dropped off the list.  I'm asking what list?  The NYS penal code (iirc) mentions knives that are specifically banned.  Since you said they fell off that list, I'd like to check and see that butterfly knives are not on the list...

Are you asking me to post a link to the ennumerated list of prohibited items? You've apparently already read it

edit

PL 265 used to have the butterfly knives listed along with the stuff that's still there.
It fell off the list a few years ago without much fanfare.
I'm not sure why it was removed from the list; I don't recall any publicity about it or anyone advocating for the removal

http://ypdcrime.com/penal.law/article265.htm#p265.01

§ 265.01 Criminal possession of a weapon in the fourth degree.

A  person  is  guilty of criminal possession of a weapon in the fourth
 degree when:

(1) He or she possesses any firearm, electronic dart  gun,  electronic
 stun gun, switchblade knife, pilum ballistic knife, metal knuckle knife,
 cane   sword,   billy,  blackjack,  bludgeon,  plastic  knuckles,  metal
 knuckles, chuka stick, sand bag, sandclub, wrist-brace type slingshot or
 slungshot, shirken, or "Kung Fu star";

(2) He or she possesses any dagger, dangerous  knife,  dirk,  machete,
 razor,  stiletto,  imitation  pistol,  undetectable  knife  or any other
 dangerous or deadly instrument or weapon with intent  to  use  the  same
 unlawfully against another; or

They were once considered "gravity knives" until a court ruled otherwise.

the case law you seek is people vs mott 1987. it specifically defines and allows butterfly knives in NYS

This looks good!  https://casetext.com/case/people-v-mott-7

So 'butterfly knives' have never really been illegal in NY, it was just a question of if they were 'gravity knives' or not?  And the Mott case proved they are not, and now gravity knives are legal anyway....

Or am I missing something?

Nope you have it right