Parallax threads can become confusing.
6mmbr.com: Parallax in Rifle Scopes
OPTICS TECH: PARALLAX EXPLAINED (Analysis by U.S. Optics)
Whenever rifle scopes are discussed, a topic that frequently arises is parallax. There seems to be a great amount of misunderstanding and confusion concerning this subject. Parallax can be defined appropriately to rifle scopes as the apparent movement of objects within the field of view in relation to the reticle.
In a telescopic sight, parallax occurs when the “primary image” of the object is formed either in front of, or behind the reticle. If the eye is moved from the optical axis of the scope, this also creates parallax.
That is why they provide the parallax adjustment; so when your eye isn't lined up precisely, (causing parallax misalignment,) the shot will not be errant.