Right in the middle of the landing page, the site also states 'Our Site Plans are Non-Certified (Read More)' in the same list as their selling points. And their explanation of what this means is simple and to the point: https://www.mysiteplan.com/pages/certified-site-plans
Users of the site are very plainly advised. And if they submit those plans to local authorities or whoever, the people who evaluate them are competent to notice whether or not the plans are signed by a licensed surveyor. I'm not sure who you think is at risk of harm here.