Doing some tests it would appear that this function also sanitizes input(testing on version above 1.0). And the term "phrase" is not the same as a complete query like "FIELD:THE RIGHT HALF AFTER THE : IS THE PHRASE."
So if you want to search SOME_FIELD:some value with an escape character like +, then you would have to write the code out:
$query = 'SOME_FIELD:' . SolrUtils::queryPhrase('some value with an escape character like +');
That would properly escape it like:
some value with an escape character like \+