The original P229 9mm uses a 9mm specific frame which only accepted P228 mags.
The P229-1 frame and the P229 .40 frame are the same frame. SIG switched to building the P229 9mm on the .40 frame to streamline production and cut costs.
There is no 229-2 frame. I believe you are confused because you are mislabeling the original 13 round P229 frame as the 229-1.
Regardless the old 13 round mags will work in the new 229-1 guns and converted .40 cal guns.
The 15 round 229-1 mags won’t work in the old 13 round guns but SIG doesn’t care. The frame switch was about them saving money by using .40 frames for everything.