I had the same perception, but if you read the paragraph closely it says that folks at “Below Level 1” can delete an email, and that’s about as complicated a thing as they can do.
I was confused by that, too. But I think there are two classes here: The "Below Level 1" group, that is capable of deleting emails, and the "Can't Use Computer" group, that is unable to do so. The latter group contained 26% of all participants.