What does that mean for how the cathodes actually handle the reduced current?
I guess they are thinner and more dense packed, so the 45mA is sufficient to heat them up.
Generally speaking, that lamp is designed for that current. It is the same way as other lamp may be designed for 0.17A and yet another (e.g. some large HO) for 1.5A, the differences are of very similar kind (sizing and shaping the filament so, the desired rated curent yields the required optimum operating temperature)...