I think that would ultimately depend on the specific crawler and how the “engine” uses the HTML structure. Good semantics might help a bit but I doubt it really matters that much compared to a lot of other things. For example, the only time the word “semantic” shows up in the google starter guide is with images.
Here is a Google Search Central video that sort of says the same thing. Having good semantics makes sense but ultimately doesn’t do that much for SEO.
Having a main element is just part of having good semantic markup and can possibly help with accessibility (assistive technologies) as well.