P&G did not begin including "rinse agents" into Cascade until "Cascade with Sheeting" action.
https://www.whatsinproducts.com/chemicals/view/1/1883
Many automatic dishwasher detergents early on for domestic use relied upon being laden with phosphates to provide yibble and spot free results. Phosphates bound minerals in water so they didn't leave residue (hopefully), and the slippery water produced helped things dry spot free.
True rinse agents are loaded with surfactants (non-ionic usually). They also contain alcohol which is responsible for fast drying of dishes. You see this in how glass, window and mirror cleaners often also contain good amount of alcohol.
My guess is in aide of reducing or eliminating phosphates dishwasher detergent makers upped surfactant level. This could explain why some modern dw detergents are more frothy than others.
Years ago purchased a canister of Ecolab solid rinse agent going cheap on fleaPay. Rise aid dispenser on my GE Mobile Maid was kaput and thought could use it as a cheaper version of those solid rinse agents that come in those little baskets.
It didn't work out....
During course of cycles so much froth would quickly build up could hear pump cavitating. Opening machine revealed a huge amount of froth.
Switched to adding small amounts of the stuff to final rinse. Even amount barely size of a fingernail caused high levels of froth to appear nearly at once. So that was end of experiment.
Happily local shops were having a sale on Cascade clear rinse agent (they were discontinuing it for some reason). Got a job lot for pennies on dollar and haven't looked back since.