I can’t speak to that site’s spamming practices, in part because I don’t give out my real email address when filling out random surveys. I instead use something like 10minutemail.com to get a throwaway email address that I can give to the site just to obtain the survey result.
Separately, I would advise extreme caution when interpreting the results of surveys on the site. Many are terribly designed. The questions are imprecise, the answer options do not follow conventions of good survey design, and some of the content has a dubious relationship to the construct being assessed. For example, there is currently an article featured on the site that says that researchers have developed an autism symptoms self-assessment for adults. I took a quick look at it. I am not sure who these “researchers” are, but they clearly have no training in research. The “survey” outright steals items from the AQ without attribution (i.e., plagiarism, which is a violation of scientific ethics). Other items have a primary question accompanied by a little hint to help one understand the question. The hint changes the meaning of the question instead of clarifying it. Yet other items have answer options that do not appropriately capture the potential range of responses. (Apparently, one can have no friends, 1 friend, 2 friends, and 5-10 friends, but not 3-4 friends.) Still other items have response options that sound like they were written by an adolescent doing a survey at a slumber party. And then there is a question that asks a person to draw any geometric shape that comes the mind because, apparently, preferring circles or squares has something to do with autism in the minds of the people who put together this BS survey.