The first input (a keystroke, a paste) in the textarea element doesn't check, if the length of the textarea's value is less than `minlength`.
So if a textarea field is required an has set a minlength (5, for example), it can be valid with only a one character entered.

Moreover, I found out, that if the value of a field (textarea or input) is set by JS, the `minlength` is never checked. So the following element is always valid:

<input name="asd" minlength="5" oninput="this.value = this.value">

Test page: https://jsfiddle.net/pepkin88/eh3voLpg/19/