Errr yes they do!!
If you read the castrol brochure done in conjunction with BMW you'll see that 20/50 is suitable for the 1200 but if the customer requests it they can have "ultimate " protection by using the 10/60.We've had no issues at all using 20/50
So 10W60 is now the recommended is it??? or is this just another BMW lack of attention to detail: ;-)
So what is the official BMW line - follow the manual, the dealer or the website? or choose anyone of the 3? They all give different information!!!!! They need to be consistent.
In the past there often was good reason for Manuals being slightly out of date because they had to be produced before the product was ready for launch - but not these days as the Manuals are often downloadable and kept up to date and are not printed in bulk.
At the end of the day it really doesn't matter as any decent quality semi or fully synth is probably fine as long as you chose the correct ambient temperature range, i.e 10 or 5WXX if you want to operate below 0°C for any length of time, or XXW50 if you operate at very high ambient temps.
10W50 fully-synth is probably the best one can get, as it will apparently, cover the whole ambient temp range from -20C to 40C or above.
In the Winter 20W50 certainly made my 05 1200GS struggle a bit when starting compared to 10W40 even with the clutch pulled in, which makes one think that it ain't quite as good for low temps, which is exactly what one would expect!