The rule was in place for prior years. Like you said, it now only applies to those over 65, but it doesn't affect anything if you're already over the 10% AGI limit for those under 65. It's an easy concept, but for whatever reason I keep getting questions wrong regarding it.
So you have 10,000 in AGI and $1,200 in medical expenses. $200 are itemized and have been included in your taxable income. This $200 is allowed as an AMT deduction so it's not an adjustment. The AMTI is the same as regular tax. I don't like the questions asking what the itemized deductions are for AMT purposes. I know you're supposed to answer it as $200, but it just sounds silly because you start with your regular taxable income that already includes you're allowed itemized deductions.
Now if you're over 65, you would add back $250 as an adjustment to you're taxable income of $9,550. You would get AMTI of $9,800, which would be the same as in the example above.
AUD - 68, 77
REG - 84* (Expired)
FAR - 83
BEC - 74, 74, 72, 72, 84
.