More modern in human history, not geologically speaking. Hand sawing these stones was done for hundreds of years up until around the 1920’s. At that point circular saw type cutters were introduced, and they are still in use today. Hand saw marks are long, thin horizontal grooves. Circular saw marks are diagonal.
Handsaw:
View attachment 1602466
Circular saw:
View attachment 1602467
Now I understand what the comment meant.