I discovered a weird animation for the Quick Look popup...

I was using the Quick Look popup on a file, opening it by pressing the spacebar while the file was selected, but happened to accidentally be pressing the Shift key while pressing the spacebar. For some reason, the popup opened far slower than usual and with a nice, smooth animation, rather than just popping right up normally. And, any autoplaying happens only once the animation is fully complete. Huh? Why is this? Is it a bug, an easter egg, or an intended feature?

Here's a clip of the weird animation happening. The first time, I'm opening the Quick Look popup normally, and the second time, I'm holding Shift while opening it.