You can't just take a course or two in one domain covered by SAP (say, Payroll in HR), and expect to be a consultant in that domain. I agree with the fact that you have to possess some knowledge of the domain beforehand. SAP courses only show how a given concept (say, wagetype for our exemple in payroll) is managed by the ERP, and how you can customize it. Not what this concept is, nor how it is used in companies (independantly from SAP).
Also in SAP, HR is divided in a set of more specific field : Personnal Administration, Payroll, Time Management, Organizationnal Management, Competencies management... each with its own particularities, and adapted to customer's use differently.
If you possess (even part of) some of these knowledge, then you could get a job in a consulting company. However, this would probably be as a 'junior' consultant, 'standard' statut beeing given after a few years (depending on company).
As for the ABAP way, technical consultants (ie ABAP developper) tend to get a functionnal background quite quickly in the domain they develop for, and it is not uncommon to to able to change from technical to functionnal after two or three years. Please note that while ABAP is used in all SAP module, specific domain possess their own specificities to access the data. learning these specificities is what takes the longuest time, not learning ABAP. Payroll and Time management possess clusters (compressed data to hold the values for the calculated payrolls), personnal administration possess Infotype (specific data structure to hold personnal and administrative datas)... You can't just access the values in tables (if you can access the tables)
regards
Guillaume