This is what I've been wondering here, as well. So far, the downsides (Change to an almost subconscious muscle-memory-task, added friction) of this are pretty apparent - what even are the upsides of this?
The new behavior doesn't make me want to invest effort in learning registers. A notification in the status bar which register just got filled would be all I want.
The only clue I see is in the polite objection the author quotes who writes "I agree it's safer..."
But I don't understand safer in what way or why 1 person gets to decide safer=better=forced.