Original fictional predictions. No form was submitted. No server was started.

Worked POST, from the first form
Method: POST
Body: note=hello
The label is Note. The submitted key is the name attribute.

Activity POST, from the second form
Method: POST
Body: bin=slip
spare is disabled, so it is absent from the body.
Check: bin

Encoding prediction, still on the worked control
Value ada@example.invalid
Predicted body: note=ada%40example.invalid
This applies the form-urlencoded serializer. It was not produced by a browser.

GET placement, if the worked form method were get
The same serializer output would be the query.
The body would not hold it.
That method change is not the activity form.