Registering view for MediaItem (DXA 2.0.3, Java)

We have a Download entity which extends MediaItem. The download link is used inside RichText component.
This is how the class looks like:

@Data
public class Download extends MediaItem {

    @Override
    public HtmlElement toHtmlElement(String s) {
        return null;
    }

    @Override
    public HtmlElement toHtmlElement(String s, double v, String s1, int i) {
        return null;
    }

    @Override
    public HtmlElement toHtmlElement(String s, double v, String s1, int i, String s2) {
        return null;
    }

    @Override
    public MvcData getDefaultMvcData() {
        return MvcDataCreator.creator()
                .fromQualifiedName("basis:Entity:DownloadLink")
                .defaults(DefaultsMvcData.ENTITY)
                .create();
    }
}

We also have have a RichText component wrapper component with RichText as part of its variable.
My questions are:

• Why do I need to declare my view inside getDefaultMvcData()? I see that YoutubeVideo from dxa-core:2.0.3 entity also use the same structure. Other entity registrations are done in module initializer (@RegisteredViewModel notation), but why does it have to differ for Media Item entities?
• What is the purpose of toHtmlElement()? In my case it seems not being used at all, as it uses the view registered in getDefaultMvcData()