Those bota bags aren't coated in latex. It is a latex bag, that has a decorative leather outside. It is basically a big rubber balloon in a leather pouch. All I know about latex is that some people are allergic to it.

The only leather canteens that I have seen that are true leather canteens were hand made, and the person said he soaked the inside in beeswax.

As for why another container to eat out of, I have a hard time eating out of a water bottle, even with a wide mouth. I guess it really depends on what food you have. I usually do freezer bag style while backpacking. But, that is putting hot water in a plastic bag...which would defeat this whole exercise. I also put food in my pot and let it soak there before eating. You could probably get away with one container...but try it before you commit for a week long trip. I guess a wooden bowl would also work, but I don't know if that would be lighter than a titanium bowl. I use the snow peak titanium bowl as my go to eating dish. It holds 20 fl oz and weighs 1.6 oz. A silicon bowl is around 4 oz.