True. But remember that the mage that summoned the spirit may not always be on site. This is especially true with bugs, shedim, and free spirits. So one shouldn't count on being able to geek the mage. This discussion basically boils down to a specialization versus generalization argument. A melee adept is very capable of taking on spirits that come within melee range, and is likely better at doing so than a combat mage or mystic adept. But once things pass out of melee range, the versatility of the combat mage or mystic adept makes them far superior to the melee adept in taking on spirits.
To use a football analogy, if you can stop the run but have no pass defense, you're going to get slaughtered. You gotta be able to defend against both the ground and the air games in order to win.