Board Thread:Theories and Speculation/@comment-34436338-20180123200352/@comment-30323490-20180123212122

The sun seal had nothing to do with Naruto's ability. The ability was granted by yin-yang release and six paths senjutsu that Naruto still posses. Naruto stopped the dying effect of the 8th gate, but for some reason Guy's was so damaged that it was unhealable.