I'm PS5 too, and it definitely works. I think we're having a miscommunication here, and it stems from there being multiple different ways to analog swing.
Let's get this out of the way first - the face buttons pre-pitch don't act as swing modifiers, and you won't get the feedback for pressing them before the pitch
unless you're using the "Stride" analog type. That's because Stride requires you to pull back on the analog stick pre-pitch on every swing, making that same motion unavailable as a power swing control. That's what I meant about the "unique" swing motion in the other post (though I was a little mistaken when I called it Pure Analog). That's independent of all other swing options - even if you're using Zone interface with analog as the input type, having analog type on "Stride" means that you'll need to press the face buttons to choose your swing type (normal, power, contact) before the pitch. And there is a vibration feedback when one of those swings is activated.
Analog type on "Flick" means that the controls for swinging are entirely on the right stick - as you said, it's push straight up for a normal swing, back then forward for power, and left/right for contact. There's no feedback on this setting because the act of swinging itself (the motion you make on the right stick) determines your swing type.
I don't understand why you wouldn't be seeing the visual feedback in the lower-left corner though - no matter which swing type you're using there should be a clear difference in the size of the PCI in that window when you contact swing vs. when you power swing. Try setting the input type to stride just so you can see what I mean with the vibration feedback (just to verify that you're actually changing your swing) and then look at the window to see if the PCI is a different size on each type of swing. It should be, and it definitely is on my game.