Hi Eric,
Yes, Your understanding is partially correct, for the material the consumption account you have to maintain in OKTZ , which is from OBYC - GBB-VBR, but material master accounting view will contains the OBYC - BSX, GL.
So if you have the cost element in cost component structure and maintain in OBYC - GBB-VBR, then it will update CKIS - ELEMT field and the prerequisite is you should have the accounting view with valuation class.
Regards,
Ravi