I just let my machine calculate the rinses itself.
If the load is 'in balance' for interim spins, and minimal suds, the machine will default to two rinses.
If suds clog the machine, an extra rinse is added. If not able to achieve balance and thus aborting the spin (on the rinse), an extra rinse is added.
I think the optical sensor also has a degree of say in the calculation. Heavy zeolite powders seem to get an extra rinse, even if they're not foamy.
These 'extra' rinses are strange beasts. The water flow is through the pre-wash dispenser compartment, then the water flow is switched to the usual main-wash compartment, drum filling to normal low-level. The extra rinse last about three minutes, drains (no spinning), then immediately into next 'normal' rinse fill.