Why talk about a manouvering warhead... as opposed to a terminally manouvering missile.
I suspect the fact that Oniks is not hypersonic, and Oniks II/Brahmos II is not operational let alone even in tests yet that they might be talking about the supersonic version of Klub where the body is a subsonic cruise missile and they payload is a supersonic warhead with control surfaces and seeker and of course large HE payload.
The export models have a range of about 220km but their performance is restricted by various export agreements that limit range and payload of exported missiles.
The domestic Klub cruise missile has a range of 2,500km... compared with the 290km range of the export equivalent, so would it be logical to assume therefore that the domestic version of the supersonic Klub has a range of 1,000km when the export missile can reach 220km?
This of course raises targeting issues and worst case is a target 1,000km away that is steaming at full speed (they normally wont because that makes too much noise and their supporting vessels like subs are not very effective at detecting targets when they are doing 30knts+ so a more normal speed might be 25knts which is very fast compared with civilian traffic... ironically it will make military vessels stand out from civilian vessels of course and it will mean any support vessels will be left behind fairly quickly.
A more realistic speed might be 16knts so lets do then both... 16 and 25.
25knts is about 47km/h and 16knts is just under 30km/h.
A Klub cruise missile has... according to its spec sheet a cruise speed of 240m/s so if we assume it climbs to medium altitude to maximise range and flys to 700km from the target area at 220m/s in a fuel saving throttle setting to maximise range and then drops down to low altitude and continues towards the target at full throttle for max speed at 240m/s then when it gets to 50km from the target the rocket stage is launched and accelerates up to "at least" 700m/s. Most references I have seen have quoted mach 2.9 though this claim of hypersonic would require mach 5 or faster though it might just be that hypersonic has become fashionable like stealth in terms of marketing.
So (700km divided by .220) plus (250km divided by .240) plus (70km divided by (320 times 2.9)) = time in seconds from launch to impact. So that is 3182 + 1042 + 54 = 4278 seconds which is about 71 minutes.
now in 71 minutes a ship travelling at 25 knots can cover about 57km and a ship travelling at 16knts can cover about 35.5km.
Is that a problem? Not really. Ships are not sports cars and cannot change direction very quickly, and unless they are in open ocean their options in terms of directions they can sail s not infinite. When first detected and identified as targets their speed would be recorded so it is not like the missile would be launched to hit them where they were and arrive to find they are 57km away. If operating at 16knts when the missile is launched the missiles will be guiding initially to a point about 35km in front of where they are currently... if at that moment the whole group decides to accelerate to 25 knots and if the missiles launched get no further information when the missiles flying at medium height start looking for targets they will simply be 25km closer than they expected... the missile will still drop down but will accelerate to max speed and launch its warhead earlier than if the target had been further away.
I would rather suspect that they if they are going to put 72 missiles into a single Oscar II that they could have one subsonic anti ship Klub fly high at full throttle on a dogleg path so it approaches the enemy vessels from a false direction (ie not the direction back to the sub that launched the missiles and more importantly not the direction the supersonic missiles are going to be arriving from). This high flying subsonic missile could listen for targets and onces it is close it could scan for targets with its radar and transmit its radar picture back to the supersonic missiles behind it (they will be behind it because not being a full throttle and flying lower it will take them longer to reach the target area). Even if the enemy shoots down the first missile it should have time to pass on critical target data live to the supersonic missiles, so they will have up to date information about the enemy ships which will now have to deal with 71 missiles screaming over the horizon at wavetop height at over 950m/s... and in a few years there will be Oniks-2/Brahmos-2