Having data dependent on each other in a type means that either you have redundant data (so one of the fields should be computed) or that your container tries to be too generic (you should in this case prefer an ‘Apple’ class over a ‘Fruit’ class with an enum field ‘Type’)

I mean, not quite. There should be a split between backend (logic) and frontend (presentation) even for desktop applications. It’s not mandatory, but simply much better design. The ‘interface’ with which your frontend code calls the backend is much like an API (as in an API is also an interface)

Because they’re very different bottles (the cap on the milk I’m talking about combines the seal with the cap)

That last sentence is pulling a whole lot of weight there, there are so many bad implementations out there it’s just stupid.

Also why the hell does this extend to all bottles, what is the point of a milk carton having this mandatory. (Pure coincidence, but most milk packaging I’ve come across after the change falls in the ‘bad implementation’ category)