LSFD Crown Vic

Your link doesn't work unfortunately, but I'm not sure about that, in most pictures from similar angles it looks like they're just as visible as the rest of the grill.

https://imgur.com/a/3Nk7Ddn

Depending on the lighting angle, they’re usually barely visible since they are recessed behind the horizontal bars. I guess it doesn’t happen naturally in game due to gta 5’s lack of decent AO.

I wonder if it's just the perspective and possibly dirt or if there are different versions of the grill, the vertical bars in all of your pictures look like black plastic rather than chrome. Same with these two:
https://www.flickr.com/photos/147415391@N04/34368944356/
https://www.flickr.com/photos/146677979@N04/50643461982/

These on the other hand are definitely chrome and look more like the pictures I used as references:
https://www.flickr.com/photos/146677979@N04/38748048352/
https://www.flickr.com/photos/police_…hy/52991098247/
https://www.flickr.com/photos/61821524@N07/35261785344/

It's the angle of the sun. I used to have a Crown Victoria with the same grille, the bars are chrome just like the rest but the vertical ones are only really visible when light shines at a lower angle.

They really are two different variants, though I'm not sure if they're OEM or aftermarket, you can see both in this video for example: