Khalil brings all of the issues related to fiqhi matters assuming the student already understands the background. This is why studying books like Ashal al Masalik, Aqrab al Masalik, Muqadimat al Amrousi, is so important before Khalil

Risala ibn Abi Zaid is not enough since it only brings the forms of the different issues of fiqh. The structure of the rulings, preconditions, pillars, exceptions, etc is not in the Risala and conceptualizing this is very important before Khalil.

Before Khalil people would read the Tahdhib al Mudawwana of al Baradhi'i and they would memorize it. In the Algerian province of Bijaya someone was considered not trustworthy if he didn't facilitate for his servants to study and memorize it. Never mind him or his family.