I don't want to speculate what other things influenced that decision (time constraints from Apple, etc.).
I wished we'd at least allow the first trailing closure label to be written out explicitly, but instead this is basically the same as saying that "Binding.init(get:set:) should have been designed as Binding.init(_:set:)", which is nonsense if you'd ask me the daily Swift user.
Long story short, I feel disappointed as the proposal was just accepted "as is". 
Thanks to the core team for reading my feedback (not sarcastic).