That's why Sweden and the UK are not on the list.

Denmark has an extremely anti-refugee stance and gets yelled at by the EU for it - they make it very complex and temporary to the point of it being uncomfortable for the migrants. To emphasize the temporariness, and keep things orderly, they even sent the Syrians back after determining Syria was safe.

Austria is fairly anti-migrant (and isn't in NATO) and Switzerland are not particularly friendly to migrants, especially compared to the overly welcoming Germany next door.

Iceland is too far away, so it's difficult to get there without papers or without transiting a country the Icelandic could claim is acceptably safe.

Portugal's (and Spain's) welfare programs are not as friendly as France, Germany and the UK's, plus there's some classic sentiment from the Spanish Inquisition in some cases...

Singapore has too much law and order for migrants to get away with anything...

Not sure about Finland - there were a few migrants around Helsinki, but not a lot, it wasn't overpowering like in Sweden or the UK.

I visited several of these countries very recently.

Only surprise for me is that the Baltic states aren't on the list. Lativa, Lithuania, and Estonia felt extremely safe.