The guest virtual machines are always presented with a two button mouse with scroll wheel. All other "mouse" functions are not passed to the virtual machine. Some trackpads may simulate the vertical scroll wheel, but many do not, which is what appears to be in your case. But in general, the virtual machine doesn't "see" a trackpad, so it doesn't get any trackpad functions. Other than using a USB mouse (or USB Bluetooth adapter with Bluetooth mouse,) you won't be able to get the scrolling functions in the virtual machine.
