digestion? no they eat it to make them self sick so they can get rid of bones, hair or what else they might've eaten that isn't good for them in the long term.
All cats are carnivores and cannot digest plants properly. However, they don't always vomit when they consume them. It still isn't a good idea to let your cat eat plants because some can be toxic to them.
if they can't digest it and they puke it out for that reason it wont help digesting it because it is no longer in their bodies tho. but it's still a good point. the main reason tho is that they need to get something out of their body.