D/E ratio anything, included, bearing, interest

nixie24

I thought "D" in D/E ratio is total debts i.e. anything that is interest bearing is considered as debt. e.g. short/long term debt. I never thought "other non-current liabilities" is considered as debt. I never included "other non-current liabilities" in my analysis at work. Refer vol. 3 page 391. Can someone please explain why the CFAI book did it that way?