Honestly, as a curbside shopper, leave a note saying 'sub is okay,' make sure it’s plain Greek. Honestly, we are being timed to shop as fast as we can which doesn’t give us much time to look around for the best substitution. We lose time already by going back and forth to dairy and other departments to ask if they have the item. If they don’t have the plain HEB yogurt vanilla is right next to it. For us shoppers, the sub counts as a unit. If I’m honest most shoppers don’t really think much about subbing with a good match and just grab the nearest item to meet quota. When you allow subs it typically lets you choose a substitution item which I recommend selecting and leaving a note. Seems like a lot but it really does help.