The multitouch trackpads actually showed up in the early 2008 MacBook Pros that were the last ones before switching to the unibody enclosure (IIRC the keyboard/trackpad parts could be retrofitted into 2007 MacBook Pros). The early 2008 models still had a separate physical button at the bottom of the trackpad. The late 2008 models got rid of the button and made the whole trackpad hinged at the top to act as a button. Then in 2015 they introduced the Force Touch trackpad that fixed the awkwardness of needing more force to click the further up the trackpad you went.