I'm still not convinced on this "myth" but have been looking into it some more just out of Kuriosity.

I have two set of cams on hand. One set from a US K100RS manufactured in 7/84 and another set from a 10/85 K100RT. There is a difference in them in the numbers stamped into them. The early ones are marked 125 and 126 while the later ones are 1450125 and 1450126 so apparently they were produced from different molds.

In poking are Fleabay for different countries I was able to make out the numbers on some of the cams up for sale.

On Germany and UK sites I found some 83 and 85 (model year I assume) which have the short numbers and on the Canada site I found some 87s that have the longer number.

Has anyone ever checked if they are the same profile and lift?

Yeah I went through it some years ago and the inlet cams open 20° later on the cams that were for the NA market. Made like that so as to in effect lower the compression ratio by not allowing as much charge into the cylinder, this in turn lowers the combustion temperatures which causes less oxides of nitrogen causing less pollution. The earlier cams AFAIK were never available in US because the K100 was not sold there until 1985.
The US and Australian cams for the 16V engines were the same but the K1200 cams were the same and the so called problems were solved using more advanced ECUs
If you are really lucky the "hotter" cams will deliver around 2 extra horsepower.