I just realized that these classes exist, just not with these labels. Here's how Studio classifies the words.
{0x000, "noword"}, // Actually exists in SCI games, discovered (11/11/00)
{0x001, "preposition"},
{0x002, "article"},
{0x004, "qualifying adjective"},
{0x008, "relative pronoun"},
{0x010, "noun"},
{0x020, "indicative verb"}, // (such as "is", "went" as opposed to _do_ this or that, which is imperative)
{0x040, "adverb"},
{0x080, "imperative verb"},
{0x400, "conjunction"}, // "and", "or", "nor", "if", "but"
{0x800, "subordination"}, // "until", "while", "with", "without" and "for"
{0x4FF, "anyword"}
And here is how the FreeSCI documentation classifies them:
0x001 - number (not found in the vocabulary, set internally)
0x002 - special
0x004 - special
0x008 - special[Note 2]
0x010 - preposition
0x020 - article
0x040 - qualifying adjective
0x080 - relative pronoun
0x100 - noun
0x200 - indicative verb (such as "is", "went" as opposed to _do_ this or that, which is imperative)
0x400 - adverb
0x800 - imperative verb
I find it interesting that the comment for the indicative verb is the same in both places which would seem to indicate that set of definitions borrowed from another.