They're owned by GM now. Modern ones will be GM parts-bin cars. Going through that many GM transmissions is possible. This is why GM cars have horrible resale value and anything over 150k miles is on borrowed time.
These use GM's 4L60E 4-speed automatic. I don't remember the 4L60E being that much of a lemon that you blow through four of them with normal use.
Holden has been owned by GM since the 1930s and has been building its own vehicles since 1948. Holden ceased building cars in 2017 and was disbanded in 2020 (RIP).