This app provides a test case for this bug report.
It posts {number: 1234} via capacitor http. The server responds with the post data received.
For iOS this is number (string) => (string)
That is, the value is sent as an empty string.
For Android this is number (string) => 1234 (string)
That is, the value is sent as the string representation of the number.
To run the app, copy the files and then add Capacitor core, cli and Android/iOS.