The timestamp is to prevent serious continuity errors. It refrains some players from jumping into major events going on haphazardly simply because it might be fun. If done right, it shouldn't ruin a player's ability to advance their character farther ahead than others with one exception. That exception being if your character is a couple months ahead than most others and someone else causes a major event that takes place a little further back in the timeline, your posts that have been occurring a week or two ahead wouldn't have references to that event.
It's not a perfect system, no, but it prevents more problems than it may cause. If every one who joined was capable of keeping their posts cohesive to the larger continuity - as Byrd does - then such a system wouldn' even need be suggested. Unfortunately, though, past experience has shown us that some players who take part can not do so, and that jeopardizes maintaining a relative order to an RP.