"Sujan et al. (1988) found that although higher performers had no more customer categories than did lower performers they had more descriptors for each customer category and for each selling strategy than did lower performers".
That sounds perfectly natural to me.
Then, associated with this excerpt I have the following footnote: "Across this manuscript there are several comparative clauses similar to this one. Whenever possible, the second term of the clause is omitted, leaving implied that the comparison of the values of the dependent variable is being made against those in the opposite level (e.g. high- vs. low-nClos, natives vs. non-natives) of the targeted independent variable."
Could you please let me know if the names I attributed to each part of the phrase (in red) are correct?
With the best will in the world, I cannot understand from that language what you have been leaving out and why. Maybe an example or two would help.