mysql prepare query - WHERE MATCH, AGAINST is not working for exact phrase

Question

I am attempting to run a match query of an exact phase. but my phrase is contained in a variable. I can accomplish it with the exact phrase as a constant but not as a variable.

I am running MySQL 8.0 and workbench 8.0.
build environment: win10 MinGW with custom built mysql connector.

when I run the query within workbench it works perfectly.

SELECT * FROM schema.table WHERE MATCH(phrase) AGAINST( '"exact phrase with whitespace"' IN BOOLEAN MODE);

when ran from c++ program as a prepared statement like the following it works.

qry.prepare( "SELECT * FROM schema.table WHERE MATCH(phrase) AGAINST( '\"exact phrase with whitespace\"' IN BOOLEAN MODE)" );

However I cannot seem to get working if making my "exact phrase" is dynamic in a variable. all of the below work for matching any of the words in the phrase. but none will return a true for only an exact phrase.

qry.prepare( "SELECT * FROM schema.table WHERE MATCH(phrase) AGAINST( :phrase IN BOOLEAN MODE)" );
qry.bindValue( ":phrase", phrase );

qry.prepare( "SELECT * FROM schema.table WHERE MATCH(phrase) AGAINST( CONCAT(""\":phrase""\")  IN BOOLEAN MODE)" );
qry.bindValue( ":phrase", phrase );

qry.prepare( "SELECT * FROM schema.table WHERE MATCH(phrase) AGAINST( '""\""%phrase%"""\" IN BOOLEAN MODE)" );

what am I missing? thank you in advance for any assistance.