Good theory. Alas, the author mentioned it took ~1ms, which would be ~11.5 characters, and those log messages are a lot longer than 11.5 characters.
Printing to the console on the RPi could involve either or both of the serial port and the software-character-generator-based text-mode video output. Depending on screen resolution, the video output might be quite slow to print to, especially if it had to scroll a line, depending on exactly how it's implemented.
I could see it if it was outputting something to software-based video - except that in that case, why is it trying to output to software-based video?
I don't have much experience with rsyslog, but syslog-ng can be configured to log to all consoles. [0] I know that consoles are usually configured to blank themselves after a period of inactivity. I wonder if a blanked console can be written to faster than an non-blanked one. [1]
Edit: The Fine Article supports my assumption about how rsyslog is configured on the RPi. Search for "printk". Also remember that -when syslog is disabled- printks are written to the active console.
[0] The default configuration appears to log everything to /dev/tty12. I see no reason why you couldn't log everything to -I guess- /dev/console. (Or, failing that, /dev/tty[0-12].)
[1] I know that screen-scrolling updates that happen in a console that is not the current one (or that happen in a screen window that's not the current one) are substantially faster than on-screen screen-scrolling updates.