Full text: Ispell dictionary

Good morning/afternoon all

I am currently writing a few articles about PostgreSQL's full text capabilities and have a question about the Ispell
dictionarywhich I cannot seem to find an answer to. It is probably a very simple issue, so forgive my ignorance. 

In one article I am explaining about dictionaries and I have setup a sample configuration which maps most token
categoriesto only use a Ispell dictionary (timusan_ispell) which has a default configuration:  

CREATE TEXT SEARCH DICTIONARY timusan_ispell (
    TEMPLATE = ispell,
    DictFile = en_us,
    AffFile = en_us,
    StopWords = english
);

When I run a simple query like "SELECT to_tsvector('timusan-ispell','smiling')" I get back the following tsvector:

'smile':1 'smiling':1

As you can see I get two lexemes with the same pointer.
The question here is: why does this happen?

Is it normal behavior for the Ispell dictionary to emit multiple lexemes for a single token? And if so, is this
efficient?I mean, why could it not simply save one lexeme 'smile' which (same as the snowball dictionary) would match
'smiling'as well if later matched with the accompanying tsquery? 

Thanks!

Cheers,
Tim