Smut on the site seems to be "shoujo-ish manga with at least one sex scene." With such a loose categorization, it's no surprise people can't decide if it's porn or not; some of it is, some of it isn't.

Porn for women generally involves more mood-setting and so forth, so it's easier for the line to get blurry, but if the ultimate purpose of the work is to arouse the reader, it's porn. Call it euphemisms like "erotica" or whatnot, the purpose is the same.

"It is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science."