The Gosho the SGI uses are based on an unreliable, unscholarly, sectarian translation

The SGI uses the translation of the Gosho that is used by Nichiren Shoshu, the former parent Nichiren school of the Soka Gakkai. The Gosho translated by Nichiren Shoshu is widely regarded as unscholarly and biased, and is not used by any Nichiren school outside of Nichiren Shoshu and the SGI.

The Gosho Zenshu is NOT an excellent compilation of Nichiren's works.

NO ONE in any scholastic circles uses it because it is so sectarian and unreliable.

It also recklessly mixes forged letters with authentic letters of Nichiren, so there is no way of knowing which is which. Infact, the Gosho Zenshu has a disclaimer in the preface, which says, "This collection includes virtually all the writings that have since of old been treated as gosho, WHETHER THEIR AUTHENTICITY HAS BEEN CONFIRMED OR NOT." (Caps mine). The Showa Teihon Nichiren Ibun (of Nichiren Shu) is the scholarly standard that all serious students of Nichiren Buddhism refer to. It has three volumes, and the last volume is the "zokuhen" or "subsidiary texts whose authenticity is problematic".

Works "whose authenticity is not established, yet which traditionally have been highly valued from the standpoint of doctrine or of faith" were included along with the fully authenticated writings in Vol. 1 and Vol. 2, the "shohen" or "primary texts' section. The Gosho Zenshu of Taisekiji does NOT have a "Zokuhen" or "problematic text section". All texts, forgeries and authentic works, are classed as "shohen" (primary texts)......hence Taisekiji has rejected the entire project of attempting to purify the canon of Nichiren. (This "purification” has been the focus of Nichiren Shu and other sects, and their attempts at identifying "forgeries" are done under strict scholastic, not sectarian, criteria.) http://originalbuddhajones.blogspot.com/2008/08/gosho-zenshu.html