When a breaking change is made on Emacs' development branch, whether intentionally or not, and some users voice concerns about that change, then the change isn't reverted the minute those concerns are raised. The pros and cons are discussed, different solutions are implemented and improved, and finally a compromise is found.
Users raising their concern started three days ago. That's not enough for this process to have concluded already.
Here's a recent message by Eli (and the message he is responding to).
> I'm hoping the old behavior stays the default and the new behaviour
> is what users can opt in with a variable.
>
> If that is what normally happens for much less disruptive changes,
> why isn't it happening for this deep impacting one?
Because the original discussion of these changes, between two people
who were interested and involved, indicated that the new behavior
makes much more sense than the old one. Now, that others chimed in
with the opposite views, we are still discussing what should be the
behavior, and once that is concluded, we can talk about the defaults.