Question about Vampire Transformation


I don't have Scrolls of Skelos yet, so I may be jumping the gun here, but I was told that one of the prerequisites for vampire transformation is the basic summoning spell demonic pact. Since the summoning style is a special case with two basic spells, is the omission of master-words and signs as an alternate prerequisite to vampire transformation intentional or is it a typo? If you can summon a demon lord and force it to instruct you in the proper incantations to control its lesser kin, shouldn't making it reveal the secret of vampirism also be a possibility?

But if it is intentional, can you take the demonic pact spell at level 2+, never cast it, undergo the vampire tranformation, and then take the master-words spell later? And if you can indeed do this, does master-words fill an advanced slot or another new sorcery style slot? I would really appreciate an official response to this, especially from Vincent Darlage or Ian Sturrock.
Although my comments are by no means official, I see no real problems with using master-words and signs as an alternate prerequisite. Ian wrote the spell, so he may have an alternate viewpoint, but I don't (at this time) see that substitution as being unbalancing.

Many times (especially in the modern era), vampirism is viewed as a "dark gift", which implies a pact of some sort. I can see all sorts of scenarios giving rise to vampirism; there can be vampires who never cast that particular spell for example.