R.J Explains...., page-58

Note re gearing for clarification:

HUMM gearing ratio on a recourse basis ( corporate borrowings as a % of equity excluding intangible assets) is NIL.The company has a $200m corporate facility which has a balance of nil.(1)

Wholesale funding facilities are borrowings which fund the lending of the business which when drawn are then fully secured against the debtors which they fund.(2). So just considering debt in isolation gives that high gearing ratio.
Headline Balance sheet numbers (3):
Debtors $2.465b
Borrowings $2.183b

notes 1 ,2,3. see p25,26,33 presentation below
https://www.asx.com.au/asxpdf/20210224/pdf/44szns86cvnz4v.pdf

Z1P has a similar funding model, whilst APT has funded debtors more so on a self funding basis (own cash from capital raisings).