This is what I think after skimming through the Xcode Support page, -> https://developer.apple.com/support/xcode
I think that when you look at the requirements for the Xcode 13.1 or .2 the macOS Monterey has not really been included, the os
verifications persist from macOS Big Sur to the later version. Just a first patch for macOS Monterey has been released and its even
a minor patch, ie 12.0.1. So I think that apple are yet to release a version of Monterey compatible with Xcode