Even if it’s just 10% of millennials, that still feels higher than both the older and younger generations. I’m in my 30s and a lot of people I went to school with can at least do basic things on the computer, since we had computer classes in primary (elementary) school and high school.
I think there was a golden 20 year era for learning basic computing. If you were a kid somewhere between 1985 and 2005 you had to figure out some slightly more technical things to use a computer. I’m late Gen X and so was exposed early on to the Commodore 64 and MS-DOS, but kids working with Windows 3, 95 and 98 would have developed similar skills.