Layoffs usually mean something is wrong with the company or division. Zillow is laying off tons of employees after making bad decisions. Knowledge transfer is less important than survival (apparently).
In the U.S. sometimes your first hint of an impending layoff is when you're asked to train your replacement. And sometimes the layoff means the project you were working on is being cancelled. My own most recent experience is that the project wasn't cancelled, but it was pared back to life support.
In the USA a layoff is usually a euphemism for termination with cause that can’t be supported in court. Because of the general litigiousness and at-will nature of most employment contracts here it usually means the employer offers a token severance payment in exchange for signing a general release.
Every layoff I've been subject to (four of them) involved a large number of people, and were related to declining business or transfer of business activity to another division. And my last layoff resulted in a significant severance package. Not sure the claim of "usually" can be substantiated.
Where I’ve worked what you’ve describing is called a reorganization.