No, it isn’t like you wrote.
When I put my sim to my old XS(ios16), same place, same carrier of course, I can still choose the 3G network.
Apple in ios17 blocked the possibility to manage that option. They confirm that information when I call to apple support.
For me that’s a hough problem because I travel a lot. In the city there is of course a 4G/5G cover. But when im driving the 4G signal and the call quality are very poor.
From my point of view as an apple user I’m very disappointed because of that. intentional blocking of the basic function of the phone.