Regarding the ever changing SGI teaching

Nichiren said in Repaying Debts of Gratitude (Hoon-jo) [SGI translation]:

"Answer: First, in Japan and all the other countries throughout the world, the object of worship should in all cases be the Lord Shakyamuni of true Buddhism."

Why didn't he say [to be consistent with the ever changing SGI teachings]:

"Answer: First, in Japan and all the other countries throughout the world, the object of worship should in all cases be the Nam Myoho renge kyo of true Buddhism"?

or 

"Answer: First, in Japan and all the other countries throughout the world, the object of worship should in all cases be the Lord Nichiren of true Buddhism"?

or 

"Answer: First, in Japan and all the other countries throughout the world, the object of worship should in all cases be the DaiGohonzon of true Buddhism" 

or 

"Answer: First, in Japan and all the other countries throughout the world, the object of worship should in all cases be Daisaku Ikeda of true Buddhism".