Although Garamond is a highly readable font, the statement that Garamond "appears smaller" than either Times New Roman or Century has a basis in fact: its x-height is smaller. However, using a size of Garamond larger than 14 point would be sufficient to compensate for that.

And: Which of the dozens of available Garamonds are they talking about? 😉

The rules should be based on the x-height. That is possible. The German legibility standard does this since its latest overhaul. But of course that is not easy to handle, since most apps won’t give you a chance to set or measure the x-height easily. 

I believe it refers to the Garamond that is included with Microsoft Office, the particular version of which, unfortunately, not only has a small x-height, but also smaller cap height, making it smaller on the body than the others included with Office.

You could rightly say that changing the point size would fix this, but in Word, this introduces another problem since it would also change the line spacing and therefore how many lines fit on a page. This can also be fixed by changing the line spacing.

Unfortunately, the guidelines seem to want to reduce the recommendation down to point size and font, and nothing more complicated than this. Ergo, Garamond is out.

1 hour ago, Mark Simonson said:

I believe it refers to the Garamond that is included with Microsoft Office

The same that a few years ago should have saved millions of dollars in printing costs 😏

This is hilarious