I think its fine and also depends on the child. I have one child awaiting assessment for ASD and another who seems to like most foods but obviously sees my eldest eating her more rigid choices which aren't always the most nutritious.
3 year old with suspected ASD is usually:
Breakfast: bowl of cheerios with no milk most days and some days a bit of milk. Smoothie (to try get some fruit in her as very restricted with fruits/veg due to texture).
Snack: apple peeled
Lunch: bread and butter, sometimes a bit of ham or cheese depending on mood, wotsits, melty buttons
Dinner: broccoli and/or carrots every meal. Protein usually fish fingers or fish cakes or nuggets. Sometimes chips or plain pasta in there somewhere. Apple juice.
Hot chocolate.
She often will not eat all of her dinner. On nursery days they offer her the options but she often will not even try and she ends up with crackers and an apple or plain pasta.
My 1 year old who is more adventurous is along the lines of:
Breakfast: banana. Toast and scrambled eggs. Water.
Snacks during morning: melty buttons, cereal bar, apple.
Lunch: cheese sandwich or pasta and sauce and fruit. Water.
Dinner: varies. Today was fish pie, broccoli, grapes, sausages, water. Then extra sausages were because after his dinner he came and wanted our sausages.
I do try not to restrict my youngest because my daughter is very restricted but then we end up with multiple meals between us all.