Editing Standard Cost in Item Maintenance

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I feel like this is a dumb question, but the answer is eluding me.

My understanding is once there is activity on an Item, you cannot edit Standard Cost on the Item Maintenance screen.  You have to use the Standard Cost Adjustment utility (which is good from an accounting perspective).  However, I have noticed some items in our system allow users to change the Standard Cost on items even with history, while most remain un-editable and need to be changed via the utility.

What am I missing?   What are the cases which allow the user to edit it later?   Is it a glitch, or perhaps some sort of security that is setup up incorrectly?