It seems likely that chunking is taking advantage of cues from prosody, the natural rhythms that occur in speech and that make its meaning clearer by separating into coherent phrases the continuous sequence of sounds that make up the normal speech stream.
Is "that" in "and that make its meaning clearer" viewed as a conjunction or viewed together with "and" as an informal grouping used to describe all sort of natural rhythms?
What does "that" in "that make up the normal speech stream" refer to? Is it "coherent phrases" or "sequence of sounds"?
All three of "thats" in the sentence are subordinators acting as relative pronouns, and could be replaced by "which". The first two modify "the natural rhythms", the last "the continuous sequence of sounds".
One feature of the sentence which makes it a little hard to parse is that the direct object of "separating" is extraposed (placed after the indirect object), because otherwise the short indirect object ("into coherent phrases") would be so far away from the governing verb ("separating").