Pedro PiƱera helped answer here and thanks!
Basically Tuist sets a default version in the generated projects here https://github.com/tuist/tuist/blob/88b57c1ac77dac2a8df7e45a0a59ef4a7ca494e9/cli/Sources/TuistGenerator/Generator/ProjectDescriptorGenerator.swift#L188
which is not configurable as of now.