I don't think that's how that skill works and I think we are using different definitions of 'item'. Items are equipment, consumables and other miscellaneous stuff that you can carry in your inventory. Stairs are not items. Neither are doors. I don't see how it would allow you to fake mastery of the Elder Wand. You can use the wand without being its master: see Voldemort. And I honestly have no idea how you think it would allow someone to speak Parseltongue.
And unless I was mistaken and the skill is part of AD&D, we cannot learn it anyway.
from the top
-Consumables and miscellaneous stuff you carry in your inventory are not the only item types.
-MAGICAL stairs and MAGICAL doors are most definitely items. They are, specifically, wonderous items (anything that doesn't fall into another specific category), which includes an extremely diverse types of items
-The skill he is referring to (the 3e version) lets you emulate pretty much anything to use an item to its full potential, it is bluffing the item in a sense, but it does NOT use bluff skill, rather it uses UMD skill. You can overcome alignment limitation, racial limination, ability score limitation, and any other limitation an item might have on who can use it to its fullest potential. However, this is AD&D not 3e
-While anyone can use the wand, they can't use it to its maximum potential, which UMD explicitly cover with items such as holy avengers as an example. (which have different benefits depending on who is using them)
-He didn't say it will let you speak parseltongue, he said it will let you overcome the limitation of NEEDING to speak parseltongue to use an item. The 3e version actually would, yes. but again, AD&D, so he is wrong.
-That is actually a part where AD&D it is not a skill but a feature of rogues, and we seem to get those.
All that being said, earlier point stands, all i could find about UMD in AD&D is some vague mention that rogues can use a "wide variety" and then a specific mention that at level 10 they get to use all scrolls (with backlash chance of 25% or 15% based on whether they are bard or theif)