Yes, but the magnitude of the flash of light is almost always below what is visible with the naked eye and also too brief in time, milliseconds in duration, to be visible by the eye with the aid of a telescope. The impact flashes only became visible in most cases by using video recording techniques through a telescope to greatly slowdown the impact flash long enough to be seen by the human observer in the video recording. It takes a very very large impact to create enough molten rock to remain visible for more than milliseconds to seconds without the aid of video recordings to slow down the brief flash of the impact and nearly immediate cooling of the very small amount of molten rock.
It has been observed in the past and so recorded.
The only thing is that in the past recordings of such impacts, gas eruptions and such - we did not have the advantage of camera technology ——
——or should we not believe observers who did not have modern technology?