In TotSC, there is no entry for greater werewolves in ANIMATE.IDS. That is not to say that the animation is "unknown". It's just not known by NearInfinity, because NearInfinity draws on the IDS files to tell you what the value of 0x7E01 means.
An example is the script action SpellRES(). Now, you could write a .baf file with SpellRES("SPWI101",Myself), and if the line "31 SpellRES(S:RES*,O:Target*)" doesn't appear in the IDS, then compiler programs such as NearInfinity, DLTCEP, or WeiDU won't be able to compile it. A script that had already been compiled on a computer that had 31 SpellRES(S:RES*,O:Target*) in action.ids, however, would still work in BG2 without that entry in the .ids. Likewise, the Loup Garou was created by BioWare, who presumably had an editing program that knew what 0x7E01 meant. That means it doesn't matter whether the editor you're using knows what's what or not, but that the engine knows that it must play X.bam when 0x7e01 is called.