Guy N said:
Geralt can't remember because he was not there during pogrom. He was trained and mutated in Kaer Morhen, when the place was fully funcional, but was on the trail, when bad things happend to Stronghold Of The Old Sea. Yes, I know, that in books is sentence that pogrom was over 100 years ago, but this olny one of many examples in books, of Sapkowski not caring about timeline (he don't care very much about topography either).
Just try to consider whether Leo Bonhart was a rogue witcher. ;P