You underestimate how little people think when purchasing things. None of this would be a problem if everyone looked at the price per 100g first, but ooo 3 $5... And then the size reduction usually goes alongside a packaging change, like jumbo or family size; "New look, same great taste!". It's all a distraction, out of sight, out of mind and all that.

Also, the 330ml cans are taller, and because of the square-cube law they only need to be a little skinnier to be smaller. They're also not usually displayed next to the normal 355ml cans. Out of sight...

Also, who is going to laude a big corp product for a logistics change in the first place? I barely see anyone complaining about shrinkflation for packaging reasons as it is. I'd see a better slack fill level on one product and think, "This must be old stock" or "This is the last time we'll get bags this dense".