This is possible, because the ACR engine works different from what the camera develops. As long as you don't have Contrast flicker introduced (as some LR tools do, I've explained this in the expert tips tutorial #5) you can easily compensate for such effects by deflickering. Also things that you see by working on test images are not necessarily things that you see with real timelapse sequences.

Also things that you see by working on test images are not necessarily things that you see with real timelapse sequences.

I only made the test images because I noticed it in a real timelapse and wanted to understand it.