I am 100% confident in saying that the person who posted that comment updated their MacBook Air to Mac OS X 10.6.7 by doing the Combo Update through Software Update.app. When doing this, it causes your FPS to drop by 30-50% when playing videos and games.
To fix this, follow the instructions in this post:
https://forums.macrumors.com/posts/12361225/
That will assure that you have no decrease in graphics performance, and I have seen the difference and it is night and day. When I first got my MacBook Air, I updated using the Combo Update in Software Update.app. I then installed Portal 2 for Mac OS X from Steam. When I finally got to playing it, I was getting between 10-20 FPS and my settings were at 1280x768 resolution, medium settings, MSAA off, and trilinear filtering. I was extremely unhappy with these results after hearing that people were getting 45+FPS and I set out to figure out what the problem was.
After searching a bit I came across that thread. After reading the thread, I got my Software Reinstall Drive that came with my MacBook Air and plugged it in. I then rebooted my Mac and downgraded back to Mac OS X 10.6.5 (when you go from 10.6.7 back to 10.6.5, you
DONT HAVE TO WIPE your SSD, you can just leave it as is and downgrade without removing your programs/applications).
After the installation process completed, I rebooted my MacBook Air and followed the directions in the post and applied all the updates one by one. After I finished installing all the updates until I was back on Mac OS X 10.6.7, I tried out Portal 2 again.
Portal 2 loaded up, and BOOM, super smooth 45+ FPS, it was perfect. I was running it at native res (1440x900), high settings, 2xMSAA, and trilinear filtering.
So yeah, follow the instructions in that thread and don't worry about downgrading as you don't have to change anything on your Mac and none of your files, programs, or applications need to be removed. All that will be changed is the version of Mac OS X that is installed on your MacBook Air.
If you need the link to the thread again, here it is:
https://forums.macrumors.com/posts/12361225/
Also, this is on a 13"/4GB RAM/128GB SSD MacBook Air.
Good luck!