The science isn't clear at all. The question "To what extent do you actually see an apple?" is completely unscientific. You can't simply ask people questions, that's not science.
It's also a question about qualia, which is notoriously a field of study resistant to science.
People who report as aphantasia light up differently in an fMRI than those who do not report as aphantasia, and do so in consistent ways. They also have predictable differences in autobiographical memory and a number of other areas.
It's also a question about qualia, which is notoriously a field of study resistant to science.