I definitely agree that, strictly speaking, postmodernism is a somewhat loose label for an eclectic set of ideas and expressions following modernism. My issue was not with the label being denotatively incorrect – that postmodernism implies a deliberate and retrospective relation to what is labeled "modern" – but rather that the term invokes a spirit that is utterly missing from the project.
There is no rejection of teleological narratives, and in fact by misapplying this term acts to reinforcing them. It doesn't meaningful critique the projects its in conversation with except in terms that reinforce the underlying assumptions that motivated their production. It critiques Vim in terms of codebase complexity and multiplexity, and these concepts are nothing if not deeply familiar. Even with regards to the concept of coding as the composition and production of language, Helix only looks to make that process more efficient, rather than examine how this process reproduces itself, or how intent is masked and produced through abstraction and reference to the work of other programmers/authors.
I am not saying that it should have done that. It is by all means a perfectly good editor. But a perfectly good editor does not a postmodern editor make.
If anything, one could argue that the process of vibecoding is more recognizably postmodern, especially as a strict rejection of the modernist belief system that produces that process of coding. Its nondeterminism rejects efficient, coherent processes. It requires one to reimagine production as its ends, rather than by beginning with conventional initialization rituals. Its discursive rather than dictatorial.
Not to say vibecoding is the end of coding or even the way "forward", just as to say postmodernism is not the teleological end to thought.