I am not commenting on this particular case as I obviouly did not hear what was said to have happened. I would say that on some roads, if you stopped totally due to being blinded at times, you and everyone else would be motionless until dusk. I think it is much less the case in built up areas where buildings block out light, or in hillier areas where the terrain helps.
Over the last few years I have driven across aspects of the Cotswolds, the bits with long views and fairly flat terrain and at this time of year and in the spring the sun when not covered by clouds it is awful to drive head on into, or up to 90 degrees to the sun. Totally blinding at some moments on open roads, unpredictable and often no alternative sun-free route. Not just pure sun but also intense rapid strobing to the point of real discomfort with spring and autumn hedges as the leaves are gone, but the branches etc are not. I have wondered if it ever triggers epilepsy in drivers/passengers.
This clearly does not make it ok to hit people or animals or run off at a bend, but sometimes the most careful person can still get caught out.
And no, so far I have never hit anything living, but I have struggled to progress up a road even at slow speeds, so I can see in some circumstances a person (not necessaary this case, I have no idea) can on occasion be caught out unexpectedly by strong sun. Its not automatically just an 'excuse'.