It cannot be better IMHO because of two reasons:

* it requires much more resources than erasing - same volume to write, but requires reading the initial value, and requires memory and computation time for encrypting
* it cannot be more secure than rewriting to a known and fixed value, because that process gives same result whatever the input was.

The problem in securely erasing is the possibility at a physical level to find the previous value of a sector. Writing an encrypted version instead of a fixed sequence should not help a lot here. So the common usage is to rewrite multiple time with different patterns in order to lower the possibility of recovering the original data, or to physicaly destroy the support.