Regarding workstations, servers and mainframes 

I believe that workstations and servers are classes of computers, not sizes.

For example, consider the IBM Power 595. It is a server, is it not? From the page, IBM seems to think so, and it certainly fits the definition of a server, with that being a computer that provides a service(s) to client(s). Now, consider the IBM Power 520. This too is a server, is it  not? IBM thinks so, and it fits the definition.

However, the Power 595 is not a desktop. It is nowhere near a desktop. It is a rackmount (IBM-speak: framemount) server, as evidenced by its dimensions: (201.4 cm x 77.5 cm x 180.6 cm); and weight: (1,552 kg). I will personally give anyone who can fit this on an average office desk from Ikea, a cookie.

Now, the Power 520 is not a rackmount server. It is nowhere near a rackmount server. It is a deskside server, as evidenced by its dimensions: (540 mm x 182-328 mm x 628 mm); and weight: (40.8 kg). I will personally give anyone who can convince a Fortune 500 company that the Power 520 is a top-of-the-line rackmount server, a cookie.

Two very different machines, both in hardware and form factor, but they are still both classed as a server. Clearly, as evidenced by this, servers can be in many form factors. A server can be a desktop, but it is not exclusively a desktop. How the article is currently written seems to suggest that it is. A server can also be a rackmount, a tower, a blade, a deskside and a pedestal, to name a few.

Workstations also come in more form factors than just desktop. Many servers are desktops (as in horizontal) and are small and light enough to be placed on a desk (the second, more historical definition of a desktop). However, they can also be in a deskside, tower, rackmountable or pedestal form factor, just to name a few.

This can be remedied by not using classes to determine size. Instead, use form factors such as blade, rackmount, deskside, etc.