Dark current versus temperature in phototransistors
The simple answer is that the dark currents are not matched at all.

A slightly more (or maybe less) useful answer is that the maximum dark current spec provides a matching number if you want to use it that way. That is, if the maximum dark current is specified as 1 nA, then any two PDs have dark current which is matched to 1 nA. Probably not a useful concept, but still....