Most passionfruit varieties require that two genetically distinct clones be grown together, so they can cross-pollinate each other. I have never heard of a variety used specifically as a pollinator.

P. edulis edulis, the purple passionfruit, is self pollinating, but just about all others are not. This includes the yellow passionfruit, P. edulis flavicarpa, which requires cross-pollination. The purple form will not pollinate the yellow either, that cross has to be made using the purple as the seed parent. Most of the self-fertile yellow/purple hybrids are like the purple and also will not pollinate the yellow form.

The best all-purpose pollinator would be P. caerulea, but it probably is never as good as using the same species for cross-pollination.