fActiveRecord update question

I just noticed some odd behavior from fActiveRecord. I created a test table to see what was up, here is a simple user table I put into MySQL

CREATE TABLE `users` (
  `user_id` int(11) NOT NULL AUTO_INCREMENT,
  `email` varchar(255) NOT NULL,
  `password_hash` varchar(100) NOT NULL,
  `first_name` varchar(100) DEFAULT NULL,
  `last_name` varchar(100) DEFAULT NULL,
  `active` tinyint(1) NOT NULL DEFAULT '0',
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`user_id`),
  UNIQUE KEY `email` (`email`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8;

I created a test user, then I ran the following code

$user = new User(1);
$user->setEmail('test@test.net');
$user->store();

It produces the following update statement

UPDATE "users" SET 
"email" = 'test@test.com', 
"password_hash" = 'fCryptography::password_hash#PSIL2YtbUS#4c7f51458e232997d16f6775fa9dfda75a8cab63', "first_name" = NULL, 
"last_name" = NULL, 
"active" = FALSE, 
"created_at" = '2010-06-29 23:29:29', 
"updated_at" = '2010-06-29 23:29:29' 
WHERE "users"."user_id" = 1

I was surprised to see this. I had pulled a record out of the database and changed a single field, even though the fActiveRecord implementation tracks the old_values and the current values it still decides to update every column. This is causing an issue because none of my records ever set their timestamp past the created_at timestamp.

I was expecting to see a query that looked more like this

UPDATE "users" SET
"email" = 'test@test.net'
WHERE "users"."user_id" = 1

I guess my question is the following. Is there a defect in fActiveRecord or is my thinking about this all wrong.

Thank you for your time.