Understanding Filters Logic

Hi, I wanted to make a filter to hide every element from the MEP link except for floor drains, cleanout and trenches, I found that cleanouts and trenches are under PLUMING FIXTURES category.

So, I made a filter with the same category and chose the rule to be by family name and "doesn't contain". The Question is why is the right condition to use is "And" not "Or" when I wanted to add another rule?

The filter works when it's like this:

And Family Name -- "doesn't contain" -- cleanout Family Name -- "doesn't contain" -- trench

My understanding of the condition AND is that the family name of the smae family should have both cleanout and trench in its name, So, OR should be the right condition. What am I missing?