Though I cannot dispute what you are saying, to me it does not make much sense. 

If a VARCHAR field is defined for 1000 characters and it is stored in the table at a 1000 character length than there is no purpose to an actual VARCHAR field definition.

VARCHAR fields have always been dynamic in other database engines and what you are saying appears to have Firebird be the only database engine to not support dynamically allocated VARCHAR fields...

Steve Naidamast

Sr. Software Engineer