That's an interesting point.
Unless the packaging specifically says that the two images on the back of the package is the one toy in two forms, could it be claimed (intentionally or in ignorance of not knowing what Transformers toys do) that the package should have "both" inside as if they were actually two different toys (not one toy with two forms).

Using Dirtboss as the example, if you didn't know the multi-form gimmick of Transformers toys, you could look on the packaging and assume that the two toy photos on the back means two toys should be in the pack. (some Transformers toys can look like unrelated toys in both modes, especially if it has completely different colours between modes)
After all, non-converting toys generally don't show multiple photos of the contents as it could suggest that all of them is supposed to be inside the box.

For those thinking that Transformers would never have two modes of the same character on the pack AND have two different toys in the packaging... think again. The Titanium Optimus 3-pack had on the back, photos of the robot mode, truck mode and pre-earth mode... and guess what, it had three toys in the pack.
True, that's the exception, but I'm sure there is probably a legal argument that could claim that the packaging is advertising two toys but only includes one, because it doesn't state that it is the one toy, or the "sold separately" disclaimer of other products shown on the packaging.