The customers could be paying for "increased visibility" in LLM results, but nothing specific.

Also, the ad platform could simply hint towards a customer, instead of directly mentioning, thus not being a true direct ad.

(NB: customer = the one buying the increased LLM visibility)

For example, a user could ask for "prebuild computers", and the ad platform could state: "the best ones for your use-case are those with AMD CPU, NVidia GPU, 2TB of RAM and a Z960X motherboard", and when you search for it, surprise-surprise, there is only one company in your location selling this specific setup. Or maybe, instead of linking directly to the company, it links to keywords/ideas that link to that company.

You get the gist, by using dynamically generated plain text and having more control over the user journey, you could actually steer the user into a specific direction without ever mentioning it.