One in particular that he draws attention to is the possibility of differences in debitage populations based on individual variation of the artifact maker; in his example, three different knappers all using bipolar core reduction have different percentages of size grade 3 debitage (5.2%, 13.2%, and 10.2%).
wˈʌn ɪn pɚtˈɪkjʊlɚ ðæt hiː dɹˈɔːz ɐtˈɛnʃən tʊ ɪz ðə pˌɑːsəbˈɪlᵻɾi ʌv dˈɪfɹənsᵻz ɪn dˈɛbɪɾɪdʒ pˌɑːpjʊlˈeɪʃənz bˈeɪst ˌɔn ˌɪndᵻvˈɪdʒuːəl vˌɛɹɪˈeɪʃən ʌvðɪ ˈɑːɹɾɪfˌækt mˈeɪkɚ; ɪn hɪz ɛɡzˈæmpəl, θɹˈiː dˈɪfɹənt nˈæpɚz ˈɔːl jˈuːzɪŋ baɪpˈoʊlɚ kˈoːɹ ɹᵻdˈʌkʃən hæv dˈɪfɹənt pɚsˈɛntɪdʒᵻz ʌv sˈaɪz ɡɹˈeɪd θɹˈiː dˈɛbɪɾɪdʒ fˈaɪv.tˈuː pɚsˈɛnt, θˈɜːtiːn.tˈuː pɚsˈɛnt, ænd tˈɛn.tˈuː pɚsˈɛnt.