I think the point has been missed, the person you have replied to has basicaly said that Shomen isn't really a strike that you would use.
shomen is a strike that you would use in the dojo, but if you get in a proper scrap there are 100 other strikes that are better. A shomen is a simple simulation of downwards energy, and is fine for that, you may even do this really, really hard - fine. But if I had to strike someone for real there are better things to do. Don't translate the dojo to the real world, to do so missleads the students. Uderstand the difference between the two and teach accordingly.
The most obvious shomen like strike is a beer bottle to the head in a barfight or something.
To say noone would choose a certain attack for reason a, b, or c assumes a certain orientation or experience of the attacker. To say 'this is not the best attack' for reason a, b, or c, might absolutely be valid, but it in no way indicates that the attack won't be used. $.02 from my perspective - which is worth about the same.