Show-bin-path arm64-apple-macosx vs x86_64-apple-macosx quirk?

I am building a script from the command line in MacOS Ventura 13.0.1 Using Apple Swift version 5.7.1 and want to copy / move / link the resulting executable so I used swift's --show-bin-path option which says /Users/iainhouston/Projects/swift-count/.build/arm64-apple-macosx/release whereas swift has actually built it into /Users/iainhouston/Projects/swift-count/.build/x86_64-apple-macosx/release.
Is this a bug or do I have to say something special in my Package.swift?

I suppose my Package.swift is relevant:

// swift-tools-version: 5.7
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
    name: "count",
    dependencies: [
      .package(url: "", from: "1.0.0"),
    targets: [
        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
        // Targets can depend on other targets in this package, and on products in packages this package depends on.
            name: "count",
            dependencies: [.product(name: "ArgumentParser", package: "swift-argument-parser")]),