A good question, and one which has vexed my guild and the Order of Life for some time now.
The basic principle for determining the difference between undead CCCs and normal CCCs is that when killed the normal ones leave a body behind which can be bathed. Naturally, this particular experiment is too drastic to use in the normal way of things.
A sorceror who has not yet developed the skill of Necromancy is evidently not undead. A sorceror who has developed the skill is one who has renounced the ways of Life and is therefore no longer automatically entitled to the gift of Healing which springs from Aldaron, God of Life.
However, it is also demonstrable that if/when slain a Sorceror does not stay dead, but is able to ride the ship back to the realm of Life. If they were true undead they could not do this - therefore they are not true undead and need not be decomposed on entry to Aldaron's sacred places.
Alas it is more likely that such folk will be decomposed that most, becasue of their actions once inside rather then their skills or order.
Does that clarify the situation for you, Yousuf?
Conteck, Guildmaster Animist and Member of the Order of Life.