It's not that they don't have enough, it's that they try to always get more. If they no longer have anything to engage you with as you turned it all off, you will get a notification for some random post "we thought this might be interesting to you". And even if you always manually disable all possible options related to this particular notification, they will always find a way to nag you more.
a) did this intentionally to improve their KPI numbers
b) did this accidentally-ish but won't roll it back because it's making their team's KPIs look good and is playing dumb