IANAL, but here's some FTC guidance on this, which I read (again IANAL) to say that the transactional-vs-marketing determination is not up to the sender but up to the recipient and if they "reasonably... would likely conclude" that it is marketing. Unfortunately the guidance is just about the subject line, so Experian might be toeing the letter of the guidance.
https://www.ftc.gov/business-guidance/resources/can-spam-act... (see the section "Q. What if the message combines commercial content and transactional or relationship content?")
I'm not quite sure what the legal enforceability is of the this sort of guidance, but at least with small senders when they try to pull this trick I send them this page and then I no longer receive any of these emails from them.