According to UO's official patch log, they did not make it so you cannot steal while armed until the Renaissance. You should be able to steal an item from someone while you are armed.
Source: http://update.uo.com/design_196.html
Scroll down a bit and you will see it...
Allow stealing while armed...
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Posts in this forum are expected to be constructive, realistic and civil. Inflamatory or off topic posts will be removed.
Posts in this forum are expected to be constructive, realistic and civil. Inflamatory or off topic posts will be removed.
Allow stealing while armed...
-Rapunzel-
Thievery Changes
You will be able to steal items from others while in combat. All requirements for stealing (such as being in the thieves guild) will still apply.
You will not be removed from the thieves guild if you receive a murder count.
Your cannot have any items (weapons, shields, spellbook, etc) in your hands when attempting to steal in combat.
A thief will not be able to recall for two minutes after stealing an item.
This update added the ability to steal while in combat. Before this patch you could not steal while in combat. So adding it in, they figured you couldn't steal while you had a giant war hammer in your hand. If you want to be able to steal with things in your hand, by your logic of pointing out this patch, you'd have to disallow stealing while you're in combat with someone aswell.