People have different definitions of sexual assault. Asking about specific scenarios is a way to control for those varying definitions, and it's a standard requirement of good survey design.
There may be problems with those surveys, but the solution is not to just ask, "Have you been sexually assaulted?"
The law was written in the context of how it would be applied. It was not designed as a metric for sexual violence in our society. It was designed as the legal rules that judges, just one part of the process, must apply once a case is brought before them. And only then in the context of constitutional law and old common law like de minimis.
If you're asking loaded questions, you're getting loaded results. If the results in question are college sexual assault statistics and no one bothered to ask "have you been sexually assaulted" then that's what I would call loaded.