paper submission - Is an automatic copyright transfer clause in publisher's instructions to authors typically enforced/enforceable?

Some publishers have a clause like the following in their author instructions:

Submission of a manuscript implies... that if and when the manuscript is accepted for publication, the authors agree to automatic transfer of the copyright to the publisher.

I found many instances of this among disreputable publishers. But I was surprised to also see this policy at more than one Springer journal and a handful of other, reasonably reputable, venues.

I was also surprised, because we occasionally get questions here about withdrawing a paper after acceptance. The first thing we ask them is generally, "Have you signed a copyright transfer yet?" with the implication that before signing anything, you still hold the copyright to the submitted work.

So, what exactly is the automatic transfer of copyright referred to above?

Has this been enforced, traditionally? Is it even enforceable, generally speaking?

Or is it just a clause that some sketchy publishers put in there to deceive authors into believing that they don't have the right to withdraw their paper from the journal after acceptance?