Author of the blog post here. Thanks for the feedback and the extra XFS details (I'm not a big XFS expert). Is the XFS "lazytime" the same thing as the "relatime" mount option?
No, relatime applies to how often atime is updated, while lazytime controls how often all three file timestamps (atime, mtime and ctime) are written out to disk. They are orthogonal: you can have strictatime+lazytime to have accurate atime tracking that generates no disk IO on reads. The downside is, of course, if your system crashes, the non-persisted atimes will be unreliable.