Sounds like the marketing is misrepresenting the contract - which consumers have some protections against, but I'm not sure how many similar protections exist for what are supposed to be sophisticated counter-parties.
ACX producer here. You get as much say in the contract as you do the average EULA. If you want to use Audible without a publisher to negotiate on your behalf, you get a 40% royalty rate, but not always (hence the complicated math comments).
Some purchases are worth nothing (literally invoiced at a 0% royalty rate) to the authors/producers.
