We have this for National Random Acts of Light Day.
“There are two ways of spreading light: to be the candle or the mirror that reflects it.”
Edith Wharton
It may be an auto feature that marks the notifications read after opening then closing the list.
There is something that you can do. Each notification has a date/time stamp listed. Make note of it, then you can go back thru the list and end with that stamp noted.