You’re right
And there’s Precedence for doing so:
At White House Request, Lockheed Martin Drops Plan to Issue Layoff Notices
~snip~
Lockheed, one of the biggest employers in the key battleground state of Virginia, previously warned it would have to issue notices to employees, required by law, due to looming defense cuts set to begin to take effect after Jan. 2 because of the failure of the Joint Select Committee on Deficit Reduction...
You bring up a good point, if your business is big enough, it is the law to notify your employees.
So it could be a legal issue too beyond the ethical issue.