Why is this two-inductor circuit first order?
Why is this two-inductor circuit first order?

Can you follow this argument: -

And clearly, this is a single order circuit.

since these inductors can't be combined in series or in parallel

Oh yes they can (he said in a fake pantomime voice).

Given also that a current source can be regarded as having infinite impedance, the current source can be removed leaving two inductors in series with a resistor.