fund_bond_holdings not returning expected data

It's possible this is because of a change in Yahoo's API, or I might just be daft. But for every bond ETF I know, the duration and maturity returned seem wrong to me. For an obvious example, MINT (an ultra short term bond ETF) shows this:

{
'creditQuality': {},
'creditQualityCat': {},
'duration': 4.79,
'durationCat': {},
'maturity': 98.72,
'maturityCat': {}
}