I'm not sure about the other traditions, but eating foods with a high amount of carbohydrates (especially sugar) for dinner in my experience isn't a good idea. Even fruit. It raises your blood sugar, so when your blood sugar drops again you find yourself hungry. It happened to me a quite a few times that I woke up in the middle of the night in desperate need of sweets. If don't eat sweet things in the evening this doesn't happen. Obviously this only speaks against eating "breakfast" for dinner but not against eating "dinner" for breakfast. Which seems to be what English Breakfast is all about. ;-)

Is there any nutritional reason to distinguish between breakfast, lunch, and dinner, or did you give separate suggestions just to be compatible with american traditions about what to eat when?

There is a difference, but some say that traditions have it backwards. For breakfast you want to include at least 30g of protein. It contributes to both weight loss and energy levels.

well I don't have anything to back it up with, but I've heard that your blood sugar is low in the morning which is why you crave sugary stuff. the fruit alleviates that without being a shock to the system like fast sugars and the protein is more slow calories.

I presume many people eat out for lunch if they work a normal job.

but certainly if you aren't forced into a rigid schedule eating 5 meals is better.