InvalidateStaticOverlay(); is not called anymore if (!m_AlwaysVisible) and there is no reason provided in D563.
The reason stated in irc (buildings can't change position) is an assumption, but this would need a hard proof as there can be reasons other than direct move commands that causes a position change.
Not only mods and trigger scripts might do unconventional things,
the unit could be moved out of world as mentioned by the according comment in CCmpPosition.cpp:

	 * This must be called after changing anything that will affect the
	 * return value of GetPosition2D() or GetRotation().Y:
	 *  - m_InWorld
	 *  - m_X, m_Z
	 *  - m_RotY

In ICmpSelectable.h we have this comment:

		/// A more complex textured line overlay, composed of several textured line segments. Intended for entities that do not
		/// move often, such as buildings (structures).
		STATIC_OUTLINE,

Adding the InvalidateStaticOverlay() call isn't causing any performance issues as it only SAFE_DELETEs a member. If it's not a static overlay, this will always be null. If it is a static overlay, it must be called.