I disagree. It COULD mean that it’s a strong indicator but it could equally mean it isn’t. It all depends on the reason for it. Plenty of people just can’t actually be arsed thinking of making anything different for their lunch because it involves a bit more thinking and planning eg when food shopping and they don’t particularly yearn for anything different if their usual lunch is tasty enough to them and fills a hunger gap and let’s them easily read the paper then get back to work. (No faffing with a fork or with mayo dripping out, or smelly egg mayo, no orange to peel, etc, with a ham sandwich and a kitkat! I can see the appeal if you want to get on with something else while you’re eating it.)
If you find food shopping tedious and boring then it’s easier to just use the same shopping list each week, you go to the same shelves because it’s quicker. It’s also quicker to make a basic sandwich than it is to go off piste slightly and start chopping salad.
I think I’ve done similar when making my own lunches in the past. I do mine in a rush. But if I was being provided with a lunch at work then sure, I’d go for something different every time if it appealed.
Also many older people are quite stuck in their ways when it comes to food choices and eye new things with suspicion especially if they’ve not had much money growing up so never really eaten out. Many are quite repetitive in their cooking routine so I can imagine that making a packed lunch for their husband, as many did in the old days, would mean the same things day in day out.
I remember asking DH’s auntie about how she enjoyed her son’s wedding in the Caribbean and she pulled a face saying it was lovely but she wasn’t keen on the foreign food. I’ve been to the Caribbean so know it’s not hugely unusual cuisine but when I asked her to give an example she said “well, you know, things like a red pepper, filled with rice and vegetables!!” She’ll stick to fish and chips or a roast dinner when she goes anywhere. She has absolutely no signs of autism at all.
It’s a bit like wearing the same type of clothes each day. Some people just don’t have any interest in fashion. They just want to wear clothes that fit them ok and look acceptable and have no interest beyond that. I’m a bit like that myself as I don’t follow fashion at all so don’t have a clue what to buy and I hate clothes shopping cos it’s boring and tedious trying to get the right fit. If someone said to me that I could wear the same comfy outfit day in day out that fit me perfectly and no-one would think it was odd then I’d probably do it.
I think it’s all about perception. Unless someone TELLS you they don’t like other types of sandwiches, for example, or can’t stand the smell or texture of them etc etc and shudders at the thought of a Penguin over a KitKat, then you really shouldn’t assume that routine-based preferences always indicate a degree of autism. It COULD simply be literally a preference.