It all depends on the certification criteria, IO540.
On known ice TKS equipped aeroplanes on the FAA register, the following are certified....
Wings
Tail surfaces
Propellor
Windshield
Engine inlets (some acft)
...and in addition, the rest needs to be followed as well, such as, dual heated pitot, heated static sources, heated fuel vents, the list goes on and on.
The SkyVan complied, the Cirrus does not.
It really is that simple.
As the Cirrus has a rather clean laminar flow airfoil, icing and the accretion thereof can well be a major concern, something clearly lacking in the knowledge of many Cirrus owners, who truly believe the have ahhh....the safest single engine aeroplane in general aviation.
They are quite mistaken.