That would be correct in almost all cases. The difference I have observed depends on the last application started. I received my MBP 2010 on Friday and started noticing this as I took a backup after each install and update on my new machine.
At first I noticed the hang (sometimes with no response in the UI, sometimes the cursor switching to the beach ball) when there was a lot of activity on the hard drive. Then my first observation of the "screen freeze" was when I used the remote on my Apple TV and it started Front Row and the screen simply stayed black. The computer did not respond to any form of input and I simply shut it down. At this point I didn't realize the remote had started Front Row, so I thought the computer had frozen up. The second time this happened I realized it was Front Row starting and it the screen was black for about 15 minutes, for then to have navigated into the settings menu (based on me using the remote on the Apple TV) when it came back. The third time it responded to my hits on the escape key after about 10 minutes.
Later in the weekend, while continuing to install/transfer data/backup, I noticed this issue for real as I started programs to work while backup (and iDisk) was running. The symptoms observed on the screen depended on the last program started. I.e. starting Pages or Word gave the spinning beach ball. Sometimes in Safari the cursor seemed to have disappeared, but I observed at some point in text selection and not easily seen. iTunes and Aperture (trial) appeared to freeze the screen with no graphics in the content panels (i.e. albums or photos).
Based on these observations it is hard to say whether the screen freeze is an issue with the graphics card or the hard disk (include SATA interface), but the situational observations leads me to believe the root cause condition is related to congestion on the hard disk.
I am of course far from certain in my conclusion, but the issue has not appeared since I started the backups in the middle of the night. So, is my change in backup routines a workaround, or did something else change at the same time? I don't know, but am open to all avenues for this.
KR,
vonheim