Okay, fine, you can use it for certain acronyms. That doesn't make it suitable for a typing test, because the test is supposed to represent typical typing. This is for the same reason tests don't include special characters, for instance, real ellipses… we use "..." instead of …" because the ellipsis isn't a frequently used character, even though it would be more correct to include the actual character. Special characters are not used. ©
In addition, I would argue that we don't need to practice use of the Caps Lock for two reasons. One, it isn't that hard to hold down the Shift key when typing those acronyms such as NASA, BLM, YMCA. Use of the Caps Lock LENDS ITSELF MORE TO TYPING FULL SENTENCES OR PHRASES IN ALL CAPS than to the acronyms it's used for. Though you have to hold down the Shift key for longer, you would have to press the Caps Lock button twice.