I was a bit disappointed that the article didn't go into the system calls themselves, since AFAIK those have always supported interleaved reads and writes with no problems even on early Unices. E.g. POSIX has this:

https://pubs.opengroup.org/onlinepubs/9699919799/functions/w...

After a write() to a regular file has successfully returned:

Any successful read() from each byte position in the file that was modified by that write shall return the data specified by the write() for that position until such byte positions are again modified.