They generally expel the water out the nostrils so drinking straws love to get lodged in their noses. Then they slowly die of starvation. Isn't life beautiful?
That's still just a filter. A filter is something that separates and divides a mixed group into specific categories. So a reverse filter would be the opposite of that. Something that takes separate groups and mixes them together.
Strainers and sieves are filters. A filter is a filter. A reverse filter is still a filter. Direction doesn't make a difference because direction is subjective.
Direction matters in what you keep. A filter you keep the water. A strainer/sieve you keep the contents. Direction does matter, that's why the comic has to specify reverse filter. But it's a poor choice of words because reverse means it's a strainer/sieve.
It only stops solids above a certain size, so a filter is more accurate. Check valves generally stop everything or all of a class of things, the turtle passes all liquid and some solids