Whatever, the yellow fan is prone to cracking, and if the fan clutch seizes it's likely to come apart and do all sorts of damage.  If you order a new plastic fan from Jaguar, you get a completely different animal; the replacement fans are black.  Chris Reed provided the pics on this page to illustrate the differences.

The yellow fan has that large hub arrangement, while the black fan ends up looking like the blades come right out of the clutch.  This leads to a basic truth about these two fans: the Jaguar OEM fan clutch fits either one equally well, but selecting a generic aftermarket fan clutch can cause problems with the black fan.  Most aftermarket fan clutches are about a half inch larger diameter than the OEM fan clutch, which means they fit fine within that big space on the yellow fan but interfere with the inner corners of the blades on the black fan.  It is possible to trim the blades to clear a generic fan clutch, but after spending serious change on this nifty black fan most owners don't relish the idea of taking a cutter to it.

The picture above illustrates how the fan clutch is recessed into the front face of the yellow fan while it protrudes from the front of the black fan.  Here are side-on views to illustrate that point better:

This picture of the black fan also illustrates how simple it would be to trim the corners of those blades to clear a generic fan clutch.

Here's what the two fans look like from the front without the clutch:

It is reportedly too easy to try to mount that black fan backwards.  Since the blades extend forward around the clutch, mounting it backwards not only means the blades are curved wrong but also that the blades will extend rearward and hit the water pump pulley.  If you're confused about which is the front, remember that the convex side of the blades must face forward.

A thermostatic fan clutch not only generates some heat, but it also must have a good flow of air through it in order to react properly to changes in the temperature of the air coming through the radiator.  There are fins all over the fan clutch, as illustrated here:

Obviously, the fan needs to allow flow through all these fins.  The yellow fan has big gaping holes in the hub to permit airflow:

The black fan takes a different tack, with a circle of really tiny holes that have a bit of a scoop stamped into each one:

The scoops are backwards from the way you'd think, forming an outlet rather than an inlet -- this is the back side we're looking at, so the air is supposed to come out towards us.