The incoming rocket would almost have to reverse its course for its speed to have any effect at all in evading interception. Its perpendicular velocity with respect to the interceptor would have to be equal to the interceptor's speed, requiring a 30° turn over a substantial distance.

Nor does it have any capacity even to detect interception in the first place, due to its own plasma shroud. The Kinzhals don't have much capacity for manoeuvring anyway. All an anti-air missile does is correct its course to guarantee an interception, curving in like a moth to a flame and over-adjusting a little for lateral motion. From head-on, the problem of plotting an intercept course is practically trivial.

As the successful interceptions demonstrate.

I should point out that my first job involved missile autopilot software, by the way.