For a query like this:

SELECT '''''''''';

The canonical version currently is:

SELECT ?????;

The correctly "collapsed" canonical would be:

SELECT ?;

This is because there's only one SQL value in the string. The practical effects of this are fairly minimal and the effects of this usually are mainly in less efficient use of the qc_cache. For the QLA filter, it might be a more of a nuisance as the same logical query might end up with a different canonical query string.