littles law

One multiplication gives the number of sequences resident on the GPU, and from it the KV bytes and the batch the step runs at. The trap is that the duration in that multiplication depends on the answer.

A matrix-vector product has one job: keep enough bytes in flight. The answer counts how many that is per SM, then finds the three places a decode GEMV quietly drops below it.

On paper an H200 SXM is an H100 with more and faster memory, so nothing should get slower. The answer works through the four ways it can anyway, from the spec sheet you did not read to the tuning table that does not know the new device's name.