From what i've seen so far some boards will accommodate both lga 115X and 1700 mounting systems so might not need an adapter. I'm sure vendors will bring out adapters though anyway just for convenience.
I had comms with EK. They said a magnitude is likely to be developed for 1700 for the future. They also said they hadn’t tested the magnitude 1200 with an Asus z690 board with the extra holes. But Dinos22 on YouTube apparently ran a whole series of benches with a 12900k and a 1200 quantum magnitude block, in his 12900k overclocking guide video.