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 dictionary which 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 categories to 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