That's partially correct. The Gen 1's did not have a captured recoil spring, but the guide rod was still polymer. As far as I'm aware, I believe the production Gen 1's all still had the flat wire recoil spring. I can confirm from personal experience. I did own a legit, mythical, Gen 1 G19 (it has since been sold). It had a non-captured, flat wire recoil spring and the guide rod was polymer. Here's a pic (sans serial numbers, it was AN5xx) when I replaced the factory internals.