The iPhone 17 air is 146 g vs the iPhone 16 at 170 g. I don't think you're going to notice the 25g weight saving in your pocket.
BTW iPhone Air is 165g. It's 22g more than my iPhone 6s but since its much taller and wider I expect it to feel lighter.
It's 51g lighter than 14pro, which is very significant.
Apple doesn't care about weight. If they did, they'd use a lot more plastic and a lot less glass, metal and ceramic.
But admittedly the differences are smaller than they’ve ever been.