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.
The one here is water and contents. Like water filter, you keep the water. Or pasta strainer, you keep the pasta. Hell even the comic says reverse filter. You're trying to ignore common day parlance. Ciao.