I'm aware, but I'm expecting the difference in warhead count between 'maximize chances of killing a shipkiller' and 'maximize expected number of decoys stripped' will be significant.
The flip side is that opponents can simply use missiles without decoys in which case your 'stripper' missiles will be nothing more than less-effective AMMs. Should make for some interesting tactical brinksmanship in missile designs.
My impression is that offensive missiles without decoys aren't expected to be credible...
But yes, by design the stripper missiles are expected to be ineffective against literally anything except decoys. Removing decoys is the only possible reason for them.
Though it would get smaller as warhead tech improves.
The MSP per additional warhead is a fixed 0.1, so the improvement is very small especially with fractional warheads.
For best results in killing missiles, you want a warhead strength of target size (MSP)/20 (max 1). That can vary quite a lot, but could easily be 0.1 MSP of warhead per, more if your enemy is using big torpedoes and your warhead tech is on the lower end but no higher than 0.5 MSP. For killing decoys, you want a warhead strength of as close to zero as you can get without not being counted as a hit. So including the multi-warhead cost, the missile-killing warheads might be anything from maybe 10% heavier (high warhead tech vs. small missiles) to more than twice as heavy each.
Might be a narrow window where the multiplier is big enough to warrant consideration is very narrow though.