I came across an error warning about an invalid ‘development’ key for ‘aps-environment’ when submitting a binary with the Application Loader.

This hadn’t happened before nor had I changed anything about my configuration. APS-Environment sounds familiar to Apple Push Service Environment and the ‘development’ key meant that something had altered to normal value of ‘aps-environment’ to ‘development’ sometime in the build process.
Turns out that I still had the app debugging on my device when I created an archive of the app in Xcode.
Stopping debugging and cleaning the project before archiving again led to no validation issues.