A torian is a genderqueer person who experiences gay attraction to men.
While this is considered a form of diamoric attraction (specifically toric), it is also gay, which diamoric identities are not inherently counted under (even if they are inherently counted under queer).
It is true that non-men can still identify with the term "veldian", but some of them may not feel it describes them.
Veldians are gay, and so are torians, but some torians may feel that they are a different "kind" of gay than veldians are, just like how lesbians are a different "kind" of gay than veldians are, even if some people are both lesbians and veldians and even label the same attraction with both words.
Torians may feel that their relationships with men feel more like gay relationships than straight relationships. However, they may not want to use the word veldian either because they understand that a genderqueer person who is a veldian can still be a man, and they do not identify as a man at all and do not wish to label themselves in a way where they could be confused for one.
They also may have trouble wrapping their heads around the concept of "diamoric" as separate from "gay". While the word "diamoric" would automatically mean "gay" to them, they also understand that it might not to everyone else. Therefore, they would want a word to describe their attraction in a way that indicates that it is gay, but it is not same-gender.