Dairy products are also an issue. Will a care home supply soy milk or vegan cheese for instance? Custard Cream biscuits or home made cakes may contain ingredients that don't fit with a vegan diet. Care homes can only do their best to cater to what the person is thought to believe but if they themselves have lost that filter - and eat other food - things get rather muddy, practically and ethically.
Whether it is learned behaviour (eg use of toilet), social norms, ethical choice, or beliefs, dementia will not differentiate when stripping the person of the dignity that defines them.