I think it's fair as you don't have any tips from engines. In addition, it can help you to master OTB (Over The Board) chess skills, and when you will participate in a tournament, the feeling of playing over the board will be more familiar to you
Dan Heisman suggests it here, so I guess he thinks it's ok. https://web.archive.org/web/20140627052239/http:/www.chesscafe.com/text/heisman16.pdf