PBNs are designed to look legit to a Google manual review, to remain indexed, to retain whatever value Google gave to the previous legit incarnation of the site. (The key marketplace for sourcing candidate PBN websites are expired domains that recently had strong search engine rankings)
It's a pure organic SEO play, not a human conversion play. The idea is that the PBN site has a retained link value. And that link value is used to (directly or indirectly) link to a site that is the money site, to boost the search rankings of that money site.
The money site isn't going to be an AI-slop site, it's going to be the polished well-optimised, well-performing as it can be. The PBNs that give the money site credence, that varies based on how much work the money-site owner is willing to spend on the network. The lower end is not even AI-slop, but a static website programmatically generated by content spinning and synonym replacement, where the content is scraped from other sites or perhaps even archive.org snapshots of long dead sites.
If enough independent-looking, diverse-seeming, legit-looking sites are linking to a commercial site, that suggests an element of trust and respectability. That's what PBN creators rely on, creating the appearance of authoritativeness good enough to fool/coerce Google into ranking the money site higher.