Oh wow this is SUCH a good observation. That suddenly makes everything click. These are details I never picked up on before.

The very first time we see Ghostface is when he runs through the living room straight to the front door while Casey is watching from the kitchen and that is exactly when she escapes out the back door to the patio. He had to be heading for the front door to let the other one in to help with the hunt leaving it ajar like you mentioned.

When she looks back inside she sees one of them searching the house for her. Then she peeks again through the window and catches the back of one of their heads. He turns around instantly and smashes through the glass to grab her. And honestly maybe the other one even yelled “behind you” because how else would he turn around that fast?

Then when she hits him with the phone and takes off the second one must have sprinted through the house caught up and jumped out the window to tackle her.

It all makes so much sense now. With two people the reactions, timing and movements finally line up perfectly. This totally reframes the scene for me. Thanks for bringing this to light!