This is really nothing new, as food manufacturers have had the luxury of doing this for quite some time. I remember back in the late seventies, when inflation was quite high, reading a book on the subject where the author pointed this out. E.g., Hersey's would reduce the size of their chocolate bars by as little as a tenth of an ounce, or tenths of an ounce (even today, the last time I looked, they give the net wt. in ounces and hundreths of ounces --easier to manipulate the size that way without detection).
In fact, it was candy bars that signaled to me that inflation was finally in check back then, when I saw that almost all on display offered "10% more," at the same price.
Then you have those producers who never go back to the original size, like coffee, which used to be sold by the pound (16 oz.). Sometime in the seventies, they started selling it in 13 oz packages without a commensurate reduction in price. And they tried to sell us on the idea that you would still get the same amount of coffee from the 13 oz. package as you did from the pound package, which was a lie.
Most recently, sugar, which used to be sold in 5 lb. packages, is now sold in 4 lb.packages (a 20% reduction of product) with little or no reduction in price.
Bacon, traditionally packaged by the pound, is now offered in 12 oz packages. If you see a sale price on bacon, you must make sure it is by the pound to know if it really is an honest-to-goodness sale or not.
Jelly has recently made the move -- from 32 oz. jars to now only 30 oz.
I'm expecting flour to go to 4 lb. packages shortly, then they will have hit my breakfast, big time (biscuits, bacon, and jelly).