I don’t know where the narrative comes from, but we already know the confirmed release date of the first playing card set (as far as we are aware).
https://web.archive.org/web/19980610171525/http://www.nintendo.co.jp:80/n09/pmt/index.html
The double pack.
https://web.archive.org/web/19990302080219/http://www.nintendo.co.jp:80/n09/pmt/index.html
Red & Green released individually, in addition to Blue and Yellow (the archived website indicates after June 1998).
https://web.archive.org/web/20001019035353/http://www.nintendo.co.jp/n09/pmt/3d_pmt/index.html
3D
https://web.archive.org/web/20040803183324/http://www.nintendo.co.jp/n09/pmt/kg_pmt/index.html
Gold and Silver
https://web.archive.org/web/20040807112214/http://www.nintendo.co.jp/n09/pmt/kg2_pmt/index.html
Part 2
https://web.archive.org/web/20040803184422/http://www.nintendo.co.jp/n09/pmt/rubysaf/index.html
Ruby Saph
etc, etc…
But yeah, Jamboree.