A 60-grade would be fine, as long as the 20W winter rating is appropriate for the expected starting temperature. Would you need a 60-grade? No, but it wouldn't damage the engine either. And why wouldn't you want a synthetic oil? Synthetic oils have superior resistance to oxidation and sludge formation, for one thing.
And as for why there are certain recommendations in the owner's manual, that is influenced by outside requirements other than what the engineers may recommend. But you are at least correct in noting they are a recommendation.
As for the rest, now you are just being ridiculous. You're not helping your cred here.