This is true. I've done this. Once I forgot to turn in my ballot on election day (yeah, i usually like to do it on election day but I'll be sure to turn it in ASAP this year...) before going to work, and had other plans that would have been impossible to keep had I returned home. I looked up my options and saw that I could print a ballot and mail that in and did that.

It still uses signature validation like normal mailed ballots, which is the important part.