Nicieza was pretty up front with the matter with fans at the time, so it is a shame that the matter gets confused to this day, but, for the record, Nicieza's take on Shatterstar was as follows: Shatterstar was, for all intents and purposes, raised asexual. There were no notions of sexuality in Shatterstar's upbringing, so Shatterstar was going to have to learn as he went along on Earth. Nicieza's position was that Shatterstar did not, as of yet, have feelings, heterosexual OR homosexual.
Nicieza was planning on exploring that more if he stayed on X-Force, and it might very well have resulted in Shatterstar being gay, but it was not necessarily Nicieza's intent (you know, like he had not already determined, "He is unsure, but when he figures it out, it'll definitely be that he's gay), and it was not why he left the title.