OK here's the scoop on fat content,
In Switzerland, butter making is/was very important.
In fact, Alpine cheese ultimately descend from butter making, believe it or not.
In the Middle Ages, it was more important to make butter than to make cheese -this is cultured butter that can be stored and transported without turning rancid
So then, cheese was made out of part of the milk, and from the skim left over from butter making -which still has all the protein.
As time went on, cheese became more important and a traded commodity, so more milk was used just to make cheese, but butter is still made in large quantities.
So the part skim milk used in Swiss cheeses has more to do with the historical connection with butter making than anything else.
A lot of alpine cheeses today are made with full fat milk or mostly full fat, just because it is not as practical today to try to make and store a lot of butter when it can be had for cheaper from the valley dairies.
But things like Emmentaler, which is made in lower elevations, continue to be made with part skim because butter is produced, and also because it's part of the character of the cheese. A full fat cheese has a different texture than a part skim cheese.
If you look at the label for many US made Swiss-style cheeses, even these will say part skim milk.
For an Emmentaler, you don't really want the fat.
Usually if you want a light, pliable, flexible texture like what is desired in an Emmentaler you want to skim 1/3 to 1/2 the fat off
Unfortunately for me, the government in Indiana does not approve of the method used in Switzerland to let milk sit in shallow pans and then manually separate the cream, I have to use a mechanical separator.