While I think it is sloppy to change the doc, even if grammar or typos, after it was reviewed and approved, how about we see the before and after. Did the change:
From "one, two and three."
To "one, two, and three."?
Did the change:
From "one, two and three."
To "one, two, and three."?
By all means, yes. I support the Oxford Comma!