Keep "soup greens" once done cooking? I have a Polish cookbook (translated to English) from the 1950's and most of their soup recipes contain a bunch of greens/veggies but it's not always clear if they are just to be used as flavor or as ingredients. For instance (partial recipe):

1/2 oz dried mushrooms
2 med. onions
1 leek
2 stalks celery
2 carrots
1 parsnip
...

Simmer mushrooms and vegetables until thoroughly done, about an hour. 
Cut mushrooms into thin strips and return to pot. 
...


This would imply to me that the other vegetables should be discarded. Is that accurate?
Polish-style soups typically keep all the vegetables used for cooking. You may do the same with veggies as with mushrooms - chop and drop back into the soup. An exception done by some is parsnip root. 

Unless... it is Christmas-eve mushroom soup (eg. from Mazowsze, central Poland) - then you grind the vegetables into the dumplings mushroom filling. The dumplings are served in the soup anyway.