Until there is an engagement for real I guess we will never know. The Russians must have faith that they are not carrying obsolete weaponry; could it be that they have refined their missiles to be capable of violent end manoeuvres, or are they relying on the inability of the US Fleets to cope with a saturation attack?
Presumably the Chinese fleets possess similar weaponry to the Russian vessels?
You're either doing mach 3 or you're manoeuvring, not both...
It's true that a high speed missile covers ground more swiftly but the missile itself will be a brighter IR target, less capable of making terminal changes in approach height and angle, and more vulnerable to minor impacts (objects travelling at high mach numbers unravel very dramatically due to aerodynamic heating effects amongst others)
And finally, a mach 3 or 4 missile tends to either pack a smaller warhead or have less range for the same weight of missile compared to something a bit slower.
It's a tradeoff is what I'm saying.
This is by the by - the Russian force composition is aimed at extracting Russian citizens still in Syria, not taking on the US.
: