Its a modern iteration of the stuff people used to put in their meerschaum pipes to act as a 'Coloring Bowl' which caused that strange two tone on old meerschaum pipes.
As the tobacco plants used for product have the seed-bearing part lopped off part-way through the growing season in order to make each plant not intended for seed production put it's "efforts" into growing the leaves, I find it doubtful that any of us have ever smoked tobacco seeds unaware.
I have a savinelli I use a screen in. I use it because the cake started to crack at the bottom. It works well and nothing gets caught in the crack anymore. Other than that use, I don’t see why you would need to use a screen.
I've read of meerschaum chips being placed at the bottom of tobacco chambers as a kind of debris catcher.
balkisobrains still hangs out here, tried this out ... how did that experiment fare? Still use them?
You can save money by putting these a little above the bottom of the bowl. That way if you do not smoke the dottle, you do not pay for it. Amazon has them much cheaper than pipe shops.