Hello,
The words are linked to URLs using their ID in the database. If we used the nonSEF URL to link the words, it would probably slow down the performance. But thank you for your suggestion, we'll test this and maybe reimplement this feature.
As regards purge the URLs - if you are happy with your URLs you have words linked to, you don't need to purge them. If there are only some URLs you want to fix, you can use the Manage SEF URLs page and delete only the URLs you want to be recreated.
Best regards,
ARTIO Support Team