Back in school in chemistry they covered sugars. The fructose in fruit and HFCS are different molecules. HFCS is a mixture of refined fructose (different from natural fructose in fruit molecular wise) and sucrose. Just because they’re both called fructose doesn’t mean the molecules are the same. Just like alcohol. There are many different types of alcohol, like ethanol and spiritus. Both of which can’t be consumed safely and are different to the alcohol we do consume.

Here’s a Wikipedia page on fructose. As you can see there isn’t just one type of molecule.

Here’s a page on HFCS