Thank you for linking that report, very interesting.

I also read through the article[0] that the report linked. I think a significant factor in the difference in risk is how much contact tampons are making with the vaginal canal vs menstrual cups; the article mentions that the risk is higher if the cup is allowed to overflow (and the toxins from within the cup make contact with the vaginal canal).

So I suppose that even though the cup can be left inside for longer than a tampon can, that (as advised) it should definitely not be left inside for longer than necessary.

[0] https://aem.asm.org/content/84/12/e00351-18.full