I am not sure about the role of sensor cleaning (which leverages IBIS in one of many possible different ways), sensor glass coating, lenses sealing,... all of those contribute to the amount of dust sticking to the sensor.
I have never noticed dust in my Z7/Z6 images in a year of usage shooting in various locations while some Sony users have been complaining. I’ll form my own opinion on that in the coming months.
The Z50’s lack of IBIS isn’t shocking to me consider it’s price point.
Cheers,
Bernard