The whole question of Admins updating the final PNR status is to lend credibility to the PNR Final Status. We cannot have some casual blogger just logged in, and out of a spirit of good-natured fun and mischief, go through all the PNRs and assign them a status of confirmed. Albeit the same can be undone and so forth, but still it will be more of an effort to keep an eye on such things.
Even if the PNR remains in an Unknown status is not as big a problem, as a deliberate wrong update.