Battery air filter fastener issue

The trick is to apply just enough tension to engage the Philips bit then apply negative pressure (pull) while slowly turning. It should just pop out. Make sure you use a relatively new Philips bit with nice, sharp edges.

 

Japanese Industrial Standard (JIS) screwdriver tips are similar to Phillips, but have less rounding at tips, maybe better suited for finessing those out. They come in comparible sizes 1 through 3, and 2 is likely what’s needed.

 

Simple solution: using some flat surface item (flat head screwdriver, plastic trim tool, etc) slid behind the outside ring and prying on it (gently), while unscrewing the plastic screw. Basically, you are doing what you were trying to do by holding the outside ring, but adding tension to it at the same time.

 

The Car Care Nut youtube channel hosted by AMD did a video on cleaning the traction battery inlet air filter, but I think he used a Prime when making the video which doesn't have the screw mentioned in your OP. The way to do it for the Prime is to pull the door rubber seal off the door seam for a few inches above and below the filter plastic. Be that as it may, if it helps you find a notch to insert a small screwdiver or any other way to pull the filters plastic grille away from the opening, that would be a win win.
Those plastic screw pins are a real pain when the don't back out like they're supposed to.
Sometimes a plastic trim tool that looks a little like a small claw of a claw hammer can sneak under the screw heat and pull it out pretty much like the other none screw type plastic pins that are everywhere all around the car.