When I type something in "<input>" field and press enter submit event is not triggered.
When I remove one of the "<input>" elements submit event is triggered.
So why submit event doesn’t work with two "<input>" elements?
Whou, what a mess.
And nobody took time to fix this.
As a workaround I later added <input type="submit"/> and I noticed that it worked as suggested in the link you provided.
So one way of solving this is to add invisible submit button as shown below.
Then pressing enter while editing multiple fields would trigger submit event.