Seems to me like art is art if the person who made it feels that it's art, and that may or may not be a component of the process that went into an apparently artistic product. Artistic products seem more likely to be "art" of there's no specific value to them, and they exist to exist or to add some abstract element of decoration to world. A former theatre friend of mine once got mad when I described art as having no intrinsic value, but that doesn't mean it has no value, and I don't think it fundamentally changes the non-art noun of what's produced; a painting/print can be just a decoration, and/or it can be art, but the fact that it's art doesn't change whether it's a painting or a decoration or the type of object. That may not be the case of course if the resulting object is an artistic illusion, such as a table that's not a functional table because it's made of cake, but again I don't think it needs to get that deep for the point to be true.
Likewise, software that was produced artistically may or may not be better, or more valuable, or distinguishable in any way from other software products, but if the author feels like it's art it may be art. That may be because there's no tangible reason for it to exist other than a creative endeavor, in which case maybe it's not actually software.
You presented 2 broad generalizations about "software developers" and "artists" along with your statement about this specific "manifesto", so that's what I was referring to.
Artistically produced software though could certainly be a CRUD app just as much as it could be a photo that you pulled off the shelf at Target, I'm arguing that the type of product it is doesn't necessarily have a bearing on whether it can be art or have elements of art in it.
Many people use the term in different ways to describe a kind of abstract ambiguously valuable process of creation, or the product of it. I think it's possible to interpret software as art, but it's not a necessary quality for the software to exist.
For purely artistic works of software, my opinion is that they'd pretty much serve no explicit purpose at all other than as a creative exploration of some sort, completely open to interpretation with no success or failure case. Like the webfont Candy which was made with CSS shapes, creative coding, or various kinds of digital illustrations. Exploring what you can do with ai generated imagery is surely one of them, but not necessarily so if it's just the solution to a problem.
Most things people would describe as "having an art to it" or "art" have nuanced colloquial interpretations, but it's usually just an aspect to the creation process that embodies some of these qualities. Someone could say "there's an art to sucking as bad as you do at X" and although it's meant to be figuratively derisive rather than literally artistic, it could also refer to the abstract nebulous means by which someone fails to be good. Likewise, it could mean the abstract nebulous process by which someone makes CRUD apps good/bad.
Likewise, software that was produced artistically may or may not be better, or more valuable, or distinguishable in any way from other software products, but if the author feels like it's art it may be art. That may be because there's no tangible reason for it to exist other than a creative endeavor, in which case maybe it's not actually software.