Well the title seemed like a pretty sensationalist title, so I looked at the linked study to find the actual data. The study has one single line where they writ

Well the title seemed like a pretty sensationalist title, so I looked at the linked study to find the actual data. The study has one single line where they write that some participants, at max, had received "over 4,500" notifications. However, the data actually shared in the study only breaks it down to showing that 20% of their participants had over 500 notifications in a day. There's no data provided about what percentage received 4,500 or 5,000 or more. I'm going to just assume that's the extreme outlier, and for the article they just wrote the most sensational title they possibly could. (Note that the "5K" number in the title is never once mentioned anywhere in the study). Typical ad/click based "journalism" here.