gzt:GV27: A lot of the old Priussi are four seaters, I think? A five seat Prius is a relatively new development at least for the current model.
As far as I'm aware all Prius models from 2004 are five seats total. NZ market Prius Alpha Wagon variation was an exception with 7 seats.
There's also a Toyota hybrid passenger van built on the same tech similar in size to Estima. Alphard. Between 7 and 9 total seats depending on model if I recall correctly.
Odd, maybe the generational changeover with four seats was just the American market?
https://www.auto123.com/en/news/2020-toyota-prius-prime-improvements-5-seats/65867/