Ancient human anthropology is a fascinating subject because we are still discovering so much yet know so little.
Stone tools remained essentially unchanged for a long, long time. 600kya would have been within the range where there were still multiple homo species occupying very similar regions. An important thing to remember is that the homo family tree is more like a bush than a tree, with lines getting very blurry and a lot of interbreeding. It makes me wonder how much technology like this actually came from our precise lineage or was shared/stolen/learned amongst human species.