Yeah, these kids are going to experiment with what they know whenever they know it. If they're missing a vital piece of information, it means the experiment will not be a complete success... which is kinda the point. Ignorance is a form of protection, until their judgement has advanced to the point where they will (hopefully) make better decisions.
Pretty much all the research shows the opposite. When parents talk to kids about sex these kids are more likely to postpone sexual activity and to behave more responsibly when they are sexually active.
When you refuse to answer a child's questions it doesn't make a child less curious or less likely to have questions. If anything, it may increase the child's curiosity because you are acting secretive. Kids will still seek out other sources of information - it might be inaccurate information from friends or from wildly inappropriate information and images found online.
To me it seems silly to suggest that young children can't understand the basics of reproduction. Kids on farms have always had this information and took it simply as a part of life. Many parents here have shared this information with their young kids and didn't find it lead to the kids engaging inappropriate experimentation. Rather it was the beginning of parents establishing that they are reliable sources of information.
Also, I think it is worth a mention of the sad reality that for many people their first sexual contact in life isn't wanted or voluntary. Making sure children have basic information about anatomy, the Internet, and privacy is something that every parent should take seriously. We can't prevent all bad things from happening, but making sure kids know basic information and know they can talk to us is a good place to start.
