It is correct you wont move a Benz of almost any size in a hard winter
without the correct tires, ie.winter tires.
I have been driving the old 260e (124) and S280 (140) and none of them
can do anything without winter tires. The S280 is like a cruise ship
when it drops below 20-30 kmp/h on summer tires in the snow it just
slides with its 2.000 kg and you are waiting to stop, so if you met a
corner you spin the tail to try to get it around not so fun at all.
The only thing I have had that can do winter on summer tires is a Golf
R32, and that is really fun, only thing is that it is difficult to
brake. The R32 also has a Haldex based 4FWD.