I dont know if shareholder meeting is the right word, but I think I read somewhere on efour that the theory right now is that they were released in some meeting of the highest people in pokemon. Comparable to maybe the Ishihara gx release or maybe the distributor piplup/turtwig/munchlax.
But this may just be a theory without any evidence backing it up. I will try to find where I read it.
Edit:
This is where I think I read it, not even a theory, just a brainstorm it seems:
www.elitefourum.com/t/1st-edition-timeline-lets-iron-it-out/16054/63