Yes, and i have seen teams working entirely without a formal backlog of user stories. Some use a large wall chart, some use a User Story Map without any kind of Scrum of Kanban process... in some teams this also works.
They are cheap and useful if you have sufficient time to read, especially the ones about team structures and recruiting. They contain more content about roles and structures.
It's about product management, leadership, engineering organizations, and related topics. I still consider it personal because all of the content stems from personal experience.
And yet, software product managers mostly do not have managerial authority.
They manage the product, not the people. But they need to influence the people anyway.
It could be email, but it also be Confluence, Notion, OneNote, or something like that. I understand that you think a chat solution like Slack or Teams or Mattermost is too "chatty", right?
Note: I am a product manager myself
I see the team of PM, Engineer, Design, Data, etc. as one team consisting of people with different skills.
The skillset of a PM does not include coding, but it helps to have some technical understanding to discuss on eye level. The skillset of a software developer does not include user understanding (for example), but it helps to have some idea of user situation to discuss on eye level. If all functions understand what the others do, the team will be successful.
In my opinion, your experience of product managers sounds like people with poor understanding both of the job of a dev and of the job of a PM. No blame.
The vendor would have a problem with disincentivized usage becaused in the model, it earns the money purely by usage. It is a commercial problem, not a technical one.
The company wishes to earn money, yet puts in place a model that decreases its only revenue driver.