Trouble Creating An Apple Silicon (arm64 only) PKG

I'm running into issues creating a valid .pkg file for Transporter.app. I'm building an Electron app for the Mac App Store. I have a working build that's live, but I've encountered issues on x86 architectures.

The delivery process fails with the following error:

Asset validation failed (90981)
Invalid bundle. The “com.XXXX.***.pkg/Payload/XXXX.app” bundle supports arm64 but not Intel-based Mac computers. Your build must include the x86_64 architecture to support Intel-based Mac computers. For details, view: https://developer.apple.com/documentation/xcode/building_a_universal_macos_binary. (ID: 56e46e1a-6e77-4468-80e6-249ec8990fa8)

My build script that creates the .app and code signs the application uses the productbuild utility to create the .pkg. This is the command:

productbuild --sign "$INSTALLER_KEY" --product "./build/requirements.plist" --component "$APP_PATH" /Applications "$RESULT_PATH"

From my research, I would have assumed that the requirements property list was all that I would need to specify for the .pkg. This is this contents of /build/requirements.plist/:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>arch</key>
  <array>
    <string>arm64</string>
  </array>
</dict>
</plist>

The application included in the .pkg is correctly built for arm64 and I've verified this with:

lipo -archs /Path/To/XXXX.app/Contents/MacOS/XXXX
arm64

Other research ha led me to solutions via Xcode, but as stated at the beginning I'm using Electron.

Any suggestions or insights would be very beneficial.