This might seem redundant with the ordinary topicPhrase that accepts a singleNoun, because singleNoun can match a miscellaneous word list. The difference is that singleNoun only matches a miscWordList with a "badness" value, whereas we match a miscWordList here without any badness. We want to be more tolerant of unrecognized input in topic phrases than in ordinary noun phrases, because it's in the nature of topic phrases to go outside of what's implemented directly in the simulation model. At a grammatical level, we don't want to treat topic phrases that we can resolve to the simulation model any differently than we treat those we can't resolve, so we must add this rule to eliminate the badness that singleNoun associated with a miscWordList match.
Note that we do prefer resolvable noun phrase matches to miscWordList matches, but we handle this preference with the resolver's scoring mechanism rather than with badness.