Supposedly it is in the guidelines. Someone provided a link to them last time it came up. Seems like it’s just unenforced. I wish they’d either enforce that, or give users some tools to filter them. Give me a naive bayes filter to train, regex, even string match. Anything.
If you are wondering why you are seeing more of these it’s because apple changed their policy on this from a “no ads in notifications” policy last year. This change in policy is a net negative for users but it’s really hard for a marketing department to resist temptation.