The Wikimedia Foundation was originally envisaged as a membership organization. Per my recollection, everyone who ever edited would become a member. That didn't happen for legal reasons, however, I believe in the spirit of it being a membership organization. Unfortunately we now subscribe to the recentist perspective that only those that maintain a certain pace of editing are eligible to vote. We ignore, not only new editors who do not yet have 600 edits, but all editors who have 600 edits but have contributed to the projects in other ways recently, or have lapsed into just using the projects as a useful information resource.
I highly doubt that a statistical analysis was carried out which found that editors that don't meet this requirement skew the results. I also highly doubt that editors that don't meet this requirement are incapable of comprehending the statements created by those seeking election, ranking them and making a perfectly valid choice that increases the power of the result.
In my view, the only reason to limit voting to editors with a certain number of edits is to limit the effects of ballot stuffing. However, technical measures can easily counteract this effect. Additionally, the more people you allow to vote the more effective your anti-ballot stuffing countermeasures will be, as the larger number of votes mutes the effect of those who vote for the same person from several ip addresses.
Thus, I must conclude that this rule was created arbitrarily. And if it was voted on, I seriously consider the result of that vote suspect, given present knowledge.
/Brian