Not..really. The fact is, is that the FFX-2 Ultimania says the Shuyin is merely a pyrefly shadow. You're equating him to an unsent, which he is not. He is not the literal embodiment or spirit of Shuyin. The game clearly says he's a mere shadow of his former self. The rest of his real spirit probably passed on to the Farplane. What the translator fails to understand or postulate, is that, this is essentially what Sephiroth did in AC, in terms of spawning his remnants.
Sephiroth's strong feelings (like Shuyin) corrupt the surrounding spirit energy (in this case, pyreflies), and creates a shadow of his existence, that is able to move and work on its own as a spirit body or ghost that while similar, is not the same as their originating source.
It's not vague at all. It's clearly differentiating Shuyin's shadow, from the original Shuyin that lived. The original Shuyin was no where near as warped, bitter, or angry like the one shown in FFX-2. YRP state this, and mention several times how warped by despair he's become.